FreeBSD: Fix docc rpath (#1228)

The docc rpath on FreeBSD included the OS version number, but the
runtimes are not installed to that location resulting in the binary
failing to launch. This fixes it to search in the correct place for the
Swift runtime libraries.

Author: etcwilde

build-script-helper.py

@@ -166,6 +166,16 @@ def get_swiftpm_options(action, args):
       # is not available.
       '-Xlinker', '-rpath', '-Xlinker', '@executable_path/../lib/swift/macosx',
     ]
+  elif build_os.startswith('freebsd'):
+    # FreeBSD triples include the OS version number.
+    # The swift runtime library install location does not, resulting in a docc
+    # that fails to launch.
+    swiftpm_args += [
+      # Library rpath for swift, dispatch, Foundation, etc. when installing
+      '-Xlinker', '-rpath', '-Xlinker', '$ORIGIN/../lib/swift/freebsd',
+    ]
+    if action == 'install':
+      swiftpm_args += ['--disable-local-rpath']
   else:
     swiftpm_args += [
       # Library rpath for swift, dispatch, Foundation, etc. when installing