compiletest: Support ignoring tests requiring missing LLVM components

[petrochenkov]

This PR implements a more principled solution to the problem described in #66084.

Builds of LLVM backends take a lot of time and disk space.
So it usually makes sense to build rustc with

[llvm]
targets = "X86"
experimental-targets = ""

unless you are working on some target-specific tasks.

A few tests, however, require non-x86 backends to be built.
A new test directive // needs-llvm-components: component1 component2 component3 makes such tests to be automatically ignored if one of the listed components is missing in the provided LLVM (this is determined through llvm-config --components).

As a result, the test suite now fully passes with LLVM built only with the x86 backend. The component list in this case is

aggressiveinstcombine all all-targets analysis asmparser asmprinter binaryformat bitreader bitstreamreader bitwriter cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine frontendopenmp fuzzmutate globalisel instcombine instrumentation interpreter ipo irreader jitlink libdriver lineeditor linker lto mc mca mcdisassembler mcjit mcparser mirparser native nativecodegen objcarcopts object objectyaml option orcerror orcjit passes profiledata remarks runtimedyld scalaropts selectiondag support symbolize tablegen target textapi transformutils vectorize windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info x86utils xray

(With the default target list it's much larger.)

aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils aggressiveinstcombine all all-targets analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine frontendopenmp fuzzmutate globalisel hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation interpreter ipo irreader jitlink libdriver lineeditor linker lto mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts object objectyaml option orcerror orcjit passes powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo riscvutils runtimedyld scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target textapi transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info x86utils xray

#66084 is also reverted now.

r? @Mark-Simulacrum

[Mark-Simulacrum]

@bors r+

[bors]

📌 Commit d3277b9 has been approved by Mark-Simulacrum

[Aaron1011]

It might be a good idea to add a flag to assert that all needed components are available, to ensure that we don't accidentally stop running these tests entirely.

[petrochenkov]

@Aaron1011

It might be a good idea to add a flag to assert that all needed components are available, to ensure that we don't accidentally stop running these tests entirely.

Addressed in #77280.

[bjorn3]

You need to use CHECK for this, right?

[petrochenkov]

Maybe. I simply reverted #66084 here and didn't make any changes.