Makefile.toolchain: Switch from cpp to $(CC) -E

Makes it more straightforward to switch to clang preprocessor later
on.

This requires a few other modifications in the Makefiles (gcc -E does
not read from stdin by default, and does not process files that do not
end in .c/.h).

BRANCH=none
BUG=chromium:854924
TEST=make buildall -j
TEST=Before and after the change, all ec.bin binaries are identical:
   git checkout m/master
   make REAL_SIGNER=dummy buildall -j
   mv build build-master
   find build-master -type d | sed -e 's/-master//' | \
         xargs -I{} mkdir -p {}
   find build-master -name ec_version.h | sed -e 's|build-master/||' | \
         xargs -I{} cp build-master/{} build/{}
   git checkout this-cl
    => comment out .PHONY: $(out)/ec_version.h in Makefiles.rules
   make REAL_SIGNER=dummy buildall -j
   find build-master -name ec.bin | sed -e 's|build-master/||' | \
         xargs -I{} diff build-master/{} build/{}
    => No difference

Change-Id: If07f033dc7e9a73245499c656562bb906dcd4130
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1117721
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

0 files changed, 0 insertions, 0 deletions