Respect user provided main-files (#646)

- add example package for C-main

Author: awvwgk

ci/run_tests.sh

@@ -98,5 +98,9 @@ pushd c_header_only
 "$fpm" build
 popd
 
+pushd c_main
+"$fpm" run
+popd
+
 # Cleanup
 rm -rf ./*/build

example_packages/c_main/app/main.c

@@ -0,0 +1,5 @@
+int
+main (void)
+{
+  return 0;
+}

example_packages/c_main/fpm.toml

@@ -0,0 +1,5 @@
+name = "c-main"
+
+[[executable]]
+name = "c-main"
+main = "main.c"

src/fpm_sources.f90

@@ -163,19 +163,23 @@ subroutine add_executable_sources(sources,executables,scope,auto_discover,error)
                 if (allocated(executables(i)%link)) then
                     sources(j)%link_libraries = executables(i)%link
                 end if
+                sources(j)%unit_type = FPM_UNIT_PROGRAM
                 cycle exe_loop
 
             end if
 
         end do
 
         ! Add if not already discovered (auto_discovery off)
-        exe_source = parse_source(join_path(executables(i)%source_dir,executables(i)%main),error)
-        exe_source%exe_name = executables(i)%name
-        if (allocated(executables(i)%link)) then
-            exe_source%link_libraries = executables(i)%link
-        end if
-        exe_source%unit_scope = scope
+        associate(exe => executables(i))
+            exe_source = parse_source(join_path(exe%source_dir,exe%main),error)
+            exe_source%exe_name = exe%name
+            if (allocated(exe%link)) then
+                exe_source%link_libraries = exe%link
+            end if
+            exe_source%unit_type = FPM_UNIT_PROGRAM
+            exe_source%unit_scope = scope
+        end associate
 
         if (allocated(error)) return