toolchain: Always use GCC for Ada sources

We can't use $(CC) in case it's set to Clang.

TEST=Built one target with Ada sources before and after this change and
     verified that the same compiler commands are emitted.

Change-Id: I9b8ea35352d74b364f09fc12d8d981ca42f8b7c8
Signed-off-by: Nico Huber <>
Tested-by: build bot (Jenkins) <>
Reviewed-by: Patrick Georgi <>
3 files changed