If you build perf in tree /xxx/treea, then cleansstate perf and build it
in /xxx/treeb having deleted treea, the build will fail, unable to find libc.
The problem is that the --sysroot option passed in through CC is missing.
This works fine if the default sysroot is ok, if it isn't, things will fail.
In 1.7 we'll start poisoning the default sysroot in gcc to catch this kind of
issue however that doesn't fix the problem with perf.
The problem is that various Makefiles set CC = $(CROSS_COMPILE)gcc. The
easist fix for now is to sed out the problematic Makefile lines. Its worth
noting the tools/lib/traceevent Makefile has a much more funky way of setting
CC which works for us and may be the way we need to fix the other Makefiles
upstream.
This fixes build failures we're occasionally seen on the autobuilders.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
