Clang 11 performs an optimization on x86_64 that is sensitive to the
presence of debug information. This results in GCC’s bootstrap failing
because it builds stage 2 with debug information and stage 3 without,
and the resulting objects do not match.
This patch uses the cctools assembler on LLVM 11 and x86_64-darwin while
using the integrated assembler on newer versions, which matches the
platform tools (Apple has uses the integrated assembler since Xcode 12).
This was not caught when cctools-llvm was added. The parens are
necessary to make sure this evaluates correctly when LLVM is new enough
to provide a compatible `otool`.
cctools-llvm is a replacement for cctools that replaces as much of cctools with equivalents from LLVM that it can reasonably do. This was motivated by wanting to reduce dependencies on cctools, which are updated infrequently by upstream.
To provide a motivating example, the version of `strip` included in cctools cannot properly strip the archives in compiler-rt in LLVM 15. Paths are left to bootstrap tools, resulting in failed requisites checks in the final stdenv build. Since `strip` needs replaced, the opportunity was taken to replace other provided they are functional replacements.
Note: This has to be done in cctools (or some equivalent) because some derivations (noteably LLVM) use the bintools of the stdenv directly instead of going through the wrapper.
The following tools from LLVM are not used in this derivation:
* LLD - not fully compatible with ld64 yet and potentially too big of a change;
* libtool - not a drop-in replacement yet because it does not support linker passthrough, which is needed by xcbuild;
* lipo - crashes when running the LLVM test suite;
* install_name_tool - fails when trying to build swift-corefoundation; and.
* randlib - not completely a drop-in replacement, so leaving it out for now.
If other incompatabilities are found, the tools can be reverted or made conditional. For example, cctools `strip` is preferred on older versions of LLVM (which lack the compiler-rt issue) or when cctools itself is a new enough version because `llvm-strip` on LLVM 11 produces files that older verions of `codesign_allocate` cannot process correctly.
One final caveat/note: Some tools are not duplicated or linked from cctools-port. The names of the tools and which ones were linked was determined based on what is provided upstream in Xcode and is installed on macOS system.
