Musl rootfs lacks libssp_nonshared for -fstack-protector

[maleadt]

I'm having some trouble building libigc for x86_64-linux-musl, whereas glibc works perfectly.
The issue I'm running into, as encountered with #743:

[ 79%] Linking CXX executable ../Release/elf_packager
cd /workspace/srcdir/intel-graphics-compiler-igc-1.0.3586/build/IGC/ElfPackager && /usr/bin/cmake -E cmake_link_script CMakeFiles/elf_packager.dir/link.txt --verbose=true
/opt/bin/x86_64-linux-musl-g++ --sysroot=/opt/x86_64-linux-musl/x86_64-linux-musl/sys-root/  -fno-exceptions -fdata-sections -ffunction-sections -O2 -pipe -fmessage-length=0 -march=corei7 -mstackrealign -fms-extensions -Werror -Wno-unused-parameter -Wno-missing-field-initializers -Wwrite-strings -Wno-long-long -Wswitch -Wno-sign-compare -Wno-unused-result -Wno-enum-compare -Wno-type-limits -Wno-ignored-qualifiers -Wformat -Wformat-security -Wno-extra -Wno-write-strings -finline -fno-strict-aliasing -msse -msse2 -msse3 -mssse3 -msse4 -msse4.1 -msse4.2 -Wno-unknown-pragmas -fPIC -D_FORTIFY_SOURCE=2 -fstack-protector -finline-functions -funswitch-loops -Wno-maybe-uninitialized -lrt -fno-rtti -fvisibility=hidden -fvisibility-inlines-hidden -DNDEBUG -g  -Wl,--gc-sections -rdynamic CMakeFiles/elf_packager.dir/main.cpp.o CMakeFiles/elf_packager.dir/__/AdaptorOCL/CLElfLib/ElfWriter.cpp.o CMakeFiles/elf_packager.dir/__/AdaptorOCL/CLElfLib/ElfReader.cpp.o  -o ../Release/elf_packager ../llvm/build/src/lib/libLLVMipo.a ../llvm/build/src/lib/libLLVMIRReader.a ../llvm/build/src/lib/libLLVMBitWriter.a ../llvm/build/src/lib/libLLVMBinaryFormat.a ../llvm/build/src/lib/libLLVMAsmParser.a ../llvm/build/src/lib/libLLVMBitReader.a ../llvm/build/src/lib/libLLVMLinker.a ../llvm/build/src/lib/libLLVMCodeGen.a ../llvm/build/src/lib/libLLVMScalarOpts.a ../llvm/build/src/lib/libLLVMTransformUtils.a ../llvm/build/src/lib/libLLVMAnalysis.a ../llvm/build/src/lib/libLLVMTarget.a ../llvm/build/src/lib/libLLVMObjCARCOpts.a ../llvm/build/src/lib/libLLVMVectorize.a ../llvm/build/src/lib/libLLVMInstrumentation.a ../llvm/build/src/lib/libLLVMObject.a ../llvm/build/src/lib/libLLVMMCParser.a ../llvm/build/src/lib/libLLVMProfileData.a ../llvm/build/src/lib/libLLVMMC.a ../llvm/build/src/lib/libLLVMCore.a ../llvm/build/src/lib/libLLVMSupport.a ../llvm/build/src/lib/libLLVMDemangle.a ../llvm/build/src/lib/libLLVMInstCombine.a ../llvm/build/src/lib/libLLVMBitstreamReader.a ../llvm/build/src/lib/libLLVMBitWriter.a ../llvm/build/src/lib/libLLVMAggressiveInstCombine.a ../llvm/build/src/lib/libLLVMTransformUtils.a ../llvm/build/src/lib/libLLVMAnalysis.a ../llvm/build/src/lib/libLLVMObject.a ../llvm/build/src/lib/libLLVMBitReader.a ../llvm/build/src/lib/libLLVMBitstreamReader.a ../llvm/build/src/lib/libLLVMMCParser.a ../llvm/build/src/lib/libLLVMMC.a ../llvm/build/src/lib/libLLVMDebugInfoCodeView.a ../llvm/build/src/lib/libLLVMDebugInfoMSF.a ../llvm/build/src/lib/libLLVMProfileData.a ../llvm/build/src/lib/libLLVMCore.a ../llvm/build/src/lib/libLLVMBinaryFormat.a ../llvm/build/src/lib/libLLVMRemarks.a ../llvm/build/src/lib/libLLVMSupport.a ../llvm/build/src/lib/libLLVMDemangle.a -lrt -ldl -lm 
/opt/x86_64-linux-musl/bin/../lib/gcc/x86_64-linux-musl/5.2.0/../../../../x86_64-linux-musl/bin/ld: cannot find -lssp_nonshared
/opt/x86_64-linux-musl/bin/../lib/gcc/x86_64-linux-musl/5.2.0/../../../../x86_64-linux-musl/bin/ld: cannot find -lssp
collect2: error: ld returned 1 exit status

This can be reduced to:

# /opt/bin/x86_64-linux-musl-g++ -fstack-protector -lrt 
/opt/x86_64-linux-musl/bin/../lib/gcc/x86_64-linux-musl/5.2.0/../../../../x86_64-linux-musl/bin/ld: cannot find -lssp_nonshared
/opt/x86_64-linux-musl/bin/../lib/gcc/x86_64-linux-musl/5.2.0/../../../../x86_64-linux-musl/bin/ld: cannot find -lssp
collect2: error: ld returned 1 exit status

Some googling around "musl ssp_nonshared" reveals I'd need to apk add musl-dev, but this is a cross build so installing native libs in the sandbox does not help me. Instead, it looks like Musl_jll should provide than just ld-musl.so it does not, e.g., Alpine's musl-dev provides several other includes and libraries: https://pkgs.alpinelinux.org/contents?branch=v3.3&name=musl-dev&arch=x86&repo=main

Can be worked around by patching away -fstack-protector

[giordano]

@Crghilardi pointed out we explicitly disable libssp on Musl:

Yggdrasil/0_RootFS/gcc_common.jl

Lines 335 to 337 in 0373033

	# On musl targets, disable a bunch of things we don't want
	if [[ "${COMPILER_TARGET}" == *-musl* ]]; then
	GCC_CONF_ARGS="${GCC_CONF_ARGS} --disable-libssp --disable-libmpx --disable-libmudflap"

I guess the why is a question for @staticfloat

[staticfloat]

I was never able to build GCC targeting musl with libssp. Perhaps support has improved, I'm not sure.