Makefile: Set retpoline cflags based on CONFIG_CC_IS_{CLANG,GCC}

This was done as part of commit 7d73c3e9c51400d3e0e755488050804e4d44737a
"Makefile: remove stale cc-option checks" upstream, and is needed to
support backporting further retpoline changes.

Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
1 file changed