[compiler-rt][CMake] Support powerpcspe build

[nemanjai]

I don't really see any issues with this but I think that @chmeee or @joerg would certainly be more qualified to approve this.

[jhibbits]

We use compiler-rt in FreeBSD for all platforms, including powerpcspe.

[pattop]

Hi Justin, I also needed D98831 and D98833 to get compiler-rt to build for a powerpcspe Linux toolchain.

[MaskRay]

Rebase: move change to compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake

compiler-rt/cmake/Modules/AllSupportedArchDefs.cmake

 set(ARM64 aarch64)
 set(ARM32 arm armhf)
 set(HEXAGON hexagon)
 set(X86 i386)
 set(X86_64 x86_64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
-set(PPC32 powerpc)
+set(PPC32 powerpc powerpcspe)
 set(PPC64 powerpc64 powerpc64le)
 set(RISCV32 riscv32)
 set(RISCV64 riscv64)
 set(S390X s390x)
 set(SPARC sparc)
 set(SPARCV9 sparcv9)
 set(WASM32 wasm32)
 set(WASM64 wasm64)

compiler-rt/cmake/builtin-config-ix.cmake

 
 set(ARM64 aarch64)
 set(ARM32 arm armhf armv6m armv7m armv7em armv7 armv7s armv7k armv8m.main armv8.1m.main)
 set(HEXAGON hexagon)
 set(X86 i386)
 set(X86_64 x86_64)
 set(MIPS32 mips mipsel)
 set(MIPS64 mips64 mips64el)
-set(PPC32 powerpc)
+set(PPC32 powerpc powerpcspe)
 set(PPC64 powerpc64 powerpc64le)
 set(RISCV32 riscv32)
 set(RISCV64 riscv64)
 set(SPARC sparc)
 set(SPARCV9 sparcv9)
 set(WASM32 wasm32)
 set(WASM64 wasm64)
 set(VE ve)

compiler-rt/lib/builtins/CMakeLists.txt

 set(mipsel_SOURCES ${mips_SOURCES})
 set(mips64_SOURCES ${GENERIC_TF_SOURCES}
                    ${mips_SOURCES})
 set(mips64el_SOURCES ${GENERIC_TF_SOURCES}
                      ${mips_SOURCES})
 
 set(powerpc_SOURCES ${GENERIC_SOURCES})
 
+set(powerpcspe_SOURCES ${GENERIC_SOURCES})
+
 set(powerpc64_SOURCES
   ppc/divtc3.c
   ppc/fixtfdi.c
   ppc/fixunstfdi.c
   ppc/floatditf.c
   ppc/floatunditf.c
   ppc/gcc_qadd.c
   ppc/gcc_qdiv.c