LLVM 9.0.0

NOTE: Newer versions are available in the superseding repo: https://github.com/ldc-developers/llvm-project/releases

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Vanilla LLVM 9.0.0 +

• LLD (03e4082, incl. a tiny workaround for LDC)
• compiler-rt libraries (e000d5e, incl. some tiny adaptations for LDC and Windows targets). Use -DCOMPILER_RT_INCLUDE_TESTS=OFF in the CMake command line to avoid the dependency on clang.
• Khronos SPIRV-LLVM-Translator library (7afffb9) to enable OpenCL emission for dcompute. Use -DLLVM_INCLUDE_TESTS=OFF in the CMake command line to avoid the dependency on clang.
• Mach-O: Support emitting the DWARF __debug_info section as non-debug section, in order to prevent the macOS linker from stripping it when linking the binary. This enables druntime's rt.backtrace to display file/line infos in backtraces. (7ce4a66)
• Windows: Use . instead of :: as CodeView debuginfo scope separator (for fully qualified names) for modules tagged with the D language, i.e., if compiling with LDC and -g. (8097236)
• Custom TLS emulation for Android. (c0a76db)