Initial version of FindMissingInclude
This allows finding missing includes for .c files (this is important
for all the cases where we generate the includes during the build
We're using GCC's -MM -MG options and iterate as long as we get
new includes. Since this would return all includes verbatim from the
#include, we check which ones are actually generated and what are
their final paths.
Note: this is currently applied only to .c files and does not (yet?)
work for .hs files (there are issues with things like ifdefs for
package versions that cause GCC to error out).
Signed-off-by: Michal Terepeta <email@example.com>