fixing build.sh not returning error in build (InfiniTimeOrg#1460)

Return the build status as return code from the `main` helper function.
In the process convert the handling if the file was sourced or directly
executed into an explicit if/else statement to make the intent clearer.

In case of an build error the error is now reported at the build step,
where the error happened.

Fixes: InfiniTimeOrg#1292

.devcontainer/build.sh

@@ -35,6 +35,8 @@ main() {
   if [ "$DISABLE_POSTBUILD" != "true" -a "$BUILD_RESULT" == 0 ]; then
     source "$BUILD_DIR/post_build.sh"
   fi
+  # assuming post_build.sh will never fail on a successful build
+  return $BUILD_RESULT
 }
 
 GetGcc() {
@@ -74,4 +76,12 @@ CmakeBuild() {
   fi
 }
 
-[[ $SOURCED == "false" ]] && main "$@" || echo "Sourced!"
+if [[ $SOURCED == "false" ]]; then
+  # It is important to return exit code of main
+  # To be future-proof, this is handled explicitely
+  main "$@"
+  BUILD_RESULT=$?
+  exit $BUILD_RESULT
+else
+  echo "Sourced!"
+fi

docker/build.sh

@@ -41,6 +41,8 @@ main() {
   if [ "$DISABLE_POSTBUILD" != "true" -a "$BUILD_RESULT" == 0 ]; then
     source "$BUILD_DIR/post_build.sh"
   fi
+  # assuming post_build.sh will never fail on a successful build
+  return $BUILD_RESULT
 }
 
 GetGcc() {
@@ -77,4 +79,12 @@ CmakeBuild() {
   fi
 }
 
-[[ $SOURCED == "false" ]] && main "$@" || echo "Sourced!"
+if [[ $SOURCED == "false" ]]; then
+  # It is important to return exit code of main
+  # To be future-proof, this is handled explicitely
+  main "$@"
+  BUILD_RESULT=$?
+  exit $BUILD_RESULT
+else
+  echo "Sourced!"
+fi