Add ASM flags virtual path for make export

When exporting a mbed project to make_armc5, the include options (-I)
of the ASM flags are not pointing to the good folder. It should be
pointing to the root mbed-os folder and not the one in BUILD.
This issue was found in the pull request ARMmbed#6168.

Signed-off-by: Hugues de Valon <[email protected]>

Author: hug-dev

tools/export/makefile/__init__.py

@@ -121,6 +121,10 @@ def generate(self):
                     'to_be_compiled']:
             ctx[key] = sorted(ctx[key])
         ctx.update(self.format_flags())
+        # Add the virtual path the the include option in the ASM flags
+        for index, flag in enumerate(ctx['asm_flags']):
+            if flag.startswith('-I'):
+                ctx['asm_flags'][index] = "-I" + ctx['vpath'][0] + "/" + ctx['asm_flags'][index][2:]
 
         for templatefile in \
             ['makefile/%s_%s.tmpl' % (self.TEMPLATE,