Remove unnecessary creation of BUILD dir for certain commands.

mbed CLI was creating the BUILD directory even in cases where it wasn't
needed. This PR deferes the creation of the BUILD dir until before
compile steps only.

Author: bridadan

mbed/mbed.py

@@ -2144,7 +2144,6 @@ def compile_(toolchain=None, target=None, profile=False, compile_library=False,
     # Find the root of the program
     program = Program(os.getcwd(), True)
     program.check_requirements(True)
-    program.ignore_build_dir()
     # Remember the original path. this is needed for compiling only the libraries and tests for the current folder.
     orig_path = os.getcwd()
 
@@ -2178,39 +2177,46 @@ def compile_(toolchain=None, target=None, profile=False, compile_library=False,
               + (['-v'] if verbose else [])
               + (list(chain.from_iterable(izip(repeat('--prefix'), config_prefix))) if config_prefix else []),
               env=env)
-    elif compile_library:
-        # Compile as a library (current dir is default)
-        if not build:
-            build = os.path.join(os.path.relpath(program.path, orig_path), program.build_dir, 'libraries', os.path.basename(orig_path), target, tchain)
-
-        popen(['python', '-u', os.path.join(tools_dir, 'build.py')]
-              + list(chain.from_iterable(izip(repeat('-D'), macros)))
-              + ['-t', tchain, '-m', target]
-              + list(chain.from_iterable(izip(repeat('--profile'), profile or [])))
-              + list(chain.from_iterable(izip(repeat('--source'), source)))
-              + ['--build', build]
-              + (['-c'] if clean else [])
-              + (['--artifact-name', artifact_name] if artifact_name else [])
-              + (['-v'] if verbose else [])
-              + args,
-              env=env)
     else:
-        # Compile as application (root is default)
+        # If the user hasn't supplied a build directory, ignore the default build directory
         if not build:
-            build = os.path.join(os.path.relpath(program.path, orig_path), program.build_dir, target, tchain)
+            program.ignore_build_dir()
+        
+        build_path = build
 
-        popen(['python', '-u', os.path.join(tools_dir, 'make.py')]
-              + list(chain.from_iterable(izip(repeat('-D'), macros)))
-              + ['-t', tchain, '-m', target]
-              + list(chain.from_iterable(izip(repeat('--profile'), profile or [])))
-              + list(chain.from_iterable(izip(repeat('--source'), source)))
-              + ['--build', build]
-              + (['-c'] if clean else [])
-              + (['--artifact-name', artifact_name] if artifact_name else [])
-              + (['--app-config', app_config] if app_config else [])
-              + (['-v'] if verbose else [])
-              + args,
-              env=env)
+        if compile_library:
+            # Compile as a library (current dir is default)
+            if not build_path:
+                build_path = os.path.join(os.path.relpath(program.path, orig_path), program.build_dir, 'libraries', os.path.basename(orig_path), target, tchain)
+
+            popen(['python', '-u', os.path.join(tools_dir, 'build.py')]
+                  + list(chain.from_iterable(izip(repeat('-D'), macros)))
+                  + ['-t', tchain, '-m', target]
+                  + list(chain.from_iterable(izip(repeat('--profile'), profile or [])))
+                  + list(chain.from_iterable(izip(repeat('--source'), source)))
+                  + ['--build', build_path]
+                  + (['-c'] if clean else [])
+                  + (['--artifact-name', artifact_name] if artifact_name else [])
+                  + (['-v'] if verbose else [])
+                  + args,
+                  env=env)
+        else:
+            # Compile as application (root is default)
+            if not build_path:
+                build_path = os.path.join(os.path.relpath(program.path, orig_path), program.build_dir, target, tchain)
+
+            popen(['python', '-u', os.path.join(tools_dir, 'make.py')]
+                  + list(chain.from_iterable(izip(repeat('-D'), macros)))
+                  + ['-t', tchain, '-m', target]
+                  + list(chain.from_iterable(izip(repeat('--profile'), profile or [])))
+                  + list(chain.from_iterable(izip(repeat('--source'), source)))
+                  + ['--build', build_path]
+                  + (['-c'] if clean else [])
+                  + (['--artifact-name', artifact_name] if artifact_name else [])
+                  + (['--app-config', app_config] if app_config else [])
+                  + (['-v'] if verbose else [])
+                  + args,
+                  env=env)
 
     program.set_defaults(target=target, toolchain=tchain)
 
@@ -2238,7 +2244,6 @@ def test_(toolchain=None, target=None, compile_list=False, run_list=False, compi
     # Find the root of the program
     program = Program(os.getcwd(), True)
     program.check_requirements(True)
-    program.ignore_build_dir()
     # Save original working directory
     orig_path = os.getcwd()
 
@@ -2257,15 +2262,16 @@ def test_(toolchain=None, target=None, compile_list=False, run_list=False, compi
             source = [program.path]
 
         # Setup the build path if not specified
-        if not build:
-            build = os.path.join(program.path, program.build_dir, 'tests', target, tchain)
+        build_path = build
+        if not build_path:
+            build_path = os.path.join(program.path, program.build_dir, 'tests', target, tchain)
 
         if test_spec:
             # Preserve path to given test spec
             test_spec = os.path.relpath(os.path.join(orig_path, test_spec), program.path)
         else:
             # Create the path to the test spec file
-            test_spec = os.path.join(build, 'test_spec.json')
+            test_spec = os.path.join(build_path, 'test_spec.json')
 
         if compile_list:
             popen(['python', '-u', os.path.join(tools_dir, 'test.py'), '--list']
@@ -2279,13 +2285,17 @@ def test_(toolchain=None, target=None, compile_list=False, run_list=False, compi
                   env=env)
 
         if compile_only or build_and_run_tests:
+            # If the user hasn't supplied a build directory, ignore the default build directory
+            if not build:
+                program.ignore_build_dir()
+
             popen(['python', '-u', os.path.join(tools_dir, 'test.py')]
                   + list(chain.from_iterable(izip(repeat('-D'), macros)))
                   + list(chain.from_iterable(izip(repeat('--profile'), profile or [])))
                   + ['-t', tchain, '-m', target]
                   + (['-c'] if clean else [])
                   + list(chain.from_iterable(izip(repeat('--source'), source)))
-                  + ['--build', build]
+                  + ['--build', build_path]
                   + ['--test-spec', test_spec]
                   + (['-n', tests_by_name] if tests_by_name else [])
                   + (['-v'] if verbose else [])
@@ -2326,7 +2336,6 @@ def export(ide=None, target=None, source=False, clean=False, supported=False):
     # Find the root of the program
     program = Program(os.getcwd(), True)
     program.check_requirements(True)
-    program.ignore_build_dir()
     # Remember the original path. this is needed for compiling only the libraries and tests for the current folder.
     orig_path = os.getcwd()
     # Change directories to the program root to use mbed OS tools
@@ -2350,6 +2359,8 @@ def export(ide=None, target=None, source=False, clean=False, supported=False):
 
     if not source or len(source) == 0:
         source = [os.path.relpath(program.path, orig_path)]
+    
+    program.ignore_build_dir()
 
     popen(['python', '-u', os.path.join(tools_dir, 'project.py')]
           + list(chain.from_iterable(izip(repeat('-D'), macros)))