[OpenMP] Provide __kmp_unnamed_critical_addr on SPARC

[rorth]

libomp.so currently fails to link on SPARC, both Solaris/sparcv9 and Linux/sparc64:

Undefined                       first referenced
 symbol                             in file
__kmp_unnamed_critical_addr         projects/openmp/runtime/src/CMakeFiles/omp.dir/kmp_gsupport.cpp.o
ld: fatal: symbol referencing errors

This patch provides the necessary definition. While at it, I noticed that on non-x86 targets the symbol wasn't marked as @object, which this patch corrects, too.

Tested on sparcv9-sun-solaris2.11, sparc64-unknown-linux-gnu, amd64-pc-solaris2.11, and x86_64-pc-linux-gnu.

[Sharjeel-Khan]

This change caused an error in Android's LLVM builders:

[5/35] Building ASM object runtime/src/CMakeFiles/omp.dir/z_Linux_asm.S.o
FAILED: runtime/src/CMakeFiles/omp.dir/z_Linux_asm.S.o 
/b/f/w/src/git/out/stage2-install/bin/clang --sysroot=/b/f/w/src/git/out/sysroots/platform/arm  -I/b/f/w/src/git/out/lib/libomp-arm-static/runtime/src -I/b/f/w/src/git/out/llvm-project/openmp/runtime/src -I/b/f/w/src/git/out/llvm-project/openmp/runtime/src/i18n -I/b/f/w/src/git/out/llvm-project/openmp/runtime/src/include -I/b/f/w/src/git/out/llvm-project/openmp/runtime/src/thirdparty/ittnotify -I/b/f/w/src/git/out/llvm-project/openmp/runtime/src/android -ffile-prefix-map=/b/f/w/src/git/= --target=armv7a-linux-androideabi30 -ffunction-sections -fdata-sections -march=armv7-a -D_LIBCPP_AVAILABILITY_HAS_NO_VERBOSE_ABORT=1 --sysroot=/b/f/w/src/git/out/sysroots/platform/arm -O3 -DNDEBUG -fPIC   -D _GNU_SOURCE -D _REENTRANT -D LIBOMP_HAVE_PTHREAD_SETNAME_NP -U_GLIBCXX_ASSERTIONS -MD -MT runtime/src/CMakeFiles/omp.dir/z_Linux_asm.S.o -MF runtime/src/CMakeFiles/omp.dir/z_Linux_asm.S.o.d -o runtime/src/CMakeFiles/omp.dir/z_Linux_asm.S.o -c /b/f/w/src/git/out/llvm-project/openmp/runtime/src/z_Linux_asm.S
/[b/f/w/src/git/out/llvm-project/openmp/runtime/src/z_Linux_asm.S:2485](https://cs.corp.google.com/piper///depot/google3/b/f/w/src/git/out/llvm-project/openmp/runtime/src/z_Linux_asm.S?l=2485):39: error: expected STT_<TYPE_IN_UPPER_CASE>, '#<type>', '%<type>' or "<type>"
    .type __kmp_unnamed_critical_addr,@object
                                                                   ^

I want to check if this error is a mistake from our build scripts or the change.

[rorth]

It's my fault, unfortunately: I'd forgotten that while the @object form works on the vast majority of ELF targets, ARM/AArch64 is the odd man out. This can be seen in the .section .note.GNU-stack definition a few lines below. I've found
that on all targets currently supported by z_Linux_asm.S, one can assemble %object instead. I'll post a (very lightly) tested patch shortly.

[mstorsjo]

It's my fault, unfortunately: I'd forgotten that while the @object form works on the vast majority of ELF targets, ARM/AArch64 is the odd man out.

I think this is only the case for ARM, not AArch64. The reason is that @ is treated as default assembler comment character there - but this isn't the case for AArch64.

[rorth]

Seems so, still %object assembles on both.