[rebranch] remove unneeded SingleCommandCompilationDatabase

[edymtt]

This is not needed anymore after swiftlang/llvm-project#3183 lands in
stable/20210726

This class will now be provided by LLVM as part of swiftlang/llvm-project#3183

[edymtt]

swiftlang/llvm-project#3183

@swift-ci please smoke-test

[edymtt]

swiftlang/llvm-project#3183

@swift-ci please smoke test

[edymtt]

swiftlang/llvm-project#3183

@swift-ci please smoke test macOS

[edymtt]

swiftlang/llvm-project#3183

@swift-ci please smoke test Windows

[edymtt]

The test failures for macOS are the same as the rebranch job

15:37:48   Swift(macosx-x86_64) :: Driver/driver-time-compilation.swift
15:37:48   Swift(macosx-x86_64) :: SILGen/let_decls.swift
15:37:48   Swift(macosx-x86_64) :: SILGen/unmanaged_ownership.swift
15:37:48   Swift(macosx-x86_64) :: SILOptimizer/array_element_propagation.sil
15:37:48   Swift(macosx-x86_64) :: SILOptimizer/array_element_propagation_ossa.sil
15:37:48   Swift(macosx-x86_64) :: SILOptimizer/mem2reg.sil
15:37:48   Swift(macosx-x86_64) :: SILOptimizer/mem2reg_ossa.sil
15:37:48   Swift(macosx-x86_64) :: SILOptimizer/super_init.swift
15:37:48   Swift(macosx-x86_64) :: api-digester/compare-dump-binary-vs-interface.swift
15:37:48   Swift(macosx-x86_64) :: api-digester/stability-stdlib-abi-with-asserts.test
15:37:48   Swift(macosx-x86_64) :: api-digester/stability-stdlib-source.swift
15:37:48   Swift(macosx-x86_64) :: stdlib/NewStringAppending.swift

[etcwilde]

That is the right (or at least known) set of failing tests. That's as close to success as we're going to get until those get fixed.
I'm not clear on "this is not needed anymore" after the other patch lands. Is that referring to this patch or the class deleted in the patch?

[edymtt]

That was referring to the class -- I reworded the PR description for better clarity.