GCC testing, precompiled headers, and CFLAGS_FOR_TARGET question

[Steve Ellcey <sellcey at cavium dot com>]

I have a question about gcc testing, precompiled header tests and the
CFLAGS_FOR_TARGET option to RUNTESTFLAGS.

I am building a complete native aarch64 toolchain (binutils, gcc, glibc) in
a non-standard location, I configure binutils and gcc with
--sysroot=/mylocation, and I want to run the gcc testsuite.

Everything mostly works, but when gcc tests are actually run, some tests
fail because the default dynamic linker, libc, and libm are used instead
of the ones I have in /mylocation/lib64.

I can work around this with:

make check RUNTESTFLAGS="CFLAGS_FOR_TARGET='-Wl,--dynamic-linker=/mylocation/lib
/ld-linux-aarch64.so.1 -Wl,-rpath=/mylocation/lib64'"

But when I do this, I noticed that a number of pch tests fail.  What I found
is that when I run the pch testsuite, it executes:

/home/sellcey/tot/obj/gcc/gcc/xgcc -B/home/sellcey/tot/obj/gcc/gcc/ ./common-1.h
 -fno-diagnostics-show-caret -fdiagnostics-color=never -O0 -g -Wl,--dynamic-link
er=/mylocation/lib/ld-linux-aarch64.so.1 -Wl,-rpath=/mylocation/lib64 -o common-
1.h.gch

And this tries to create an executable instead of a pre-compiled header.
If I run the same command without the -Wl flags then GCC creates the
pre-compiled header that I need for testing.

Is it excpected that GCC changes from creating a pch to creating an executable
when it see -Wl flags?  Is there a flag that we can use to explicitly tell GCC
that we want to create a precompiled header in this instance?

Steve Ellcey
sellcey@cavium.com