The build fails with:
```console
module/evdi_fb.c: In function 'evdifb_create':
module/evdi_fb.c:427:21:
error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
427 | info->fbops = efbdev->fb_ops;
| ^
````
A resolution is to treat discard-qualifiers warnings as non-error.
See https://hydra.nixos.org/build/239848621
darwin.cctools defaults to `llvm-strip` when the version of LLVM in the
stdenv is 12 or newer. This strip implementation does not support the
`-c` flag required by older versions of GCC. Use the cctools-port
version for compatibility when building older versions of GCC.
The x86_64-darwin build fails with the following symbol errors when
building gencondmd:
Undefined symbols for architecture x86_64:
"_ix86_excess_precision", referenced from:
___cxx_global_var_init.101 in gencondmd.o
"_ix86_fpmath", referenced from:
___cxx_global_var_init.101 in gencondmd.o
"_ix86_isa_flags", referenced from:
___cxx_global_var_init.101 in gencondmd.o
"_ix86_unsafe_math_optimizations", referenced from:
___cxx_global_var_init.101 in gencondmd.o
"_target_flags", referenced from:
___cxx_global_var_init.101 in gencondmd.o
This commit applies a workaround posted to the GCC BugZilla.
See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92061.
Darwin uses the clang integrated assembler, which does not support
`--gstabs`. While the `configure` script detects whether the assembler
supports it, Darwin passes `--gstabs` unconditionally. This patch is
backported to make the bootstrap only use it when supported.
Older versions of GCC use `-pipe` on Darwin due to compatibility
problems with older cctools assemblers. Darwin now uses the clang
integrated assembler. While it is possible to pipe input into it, the
wrapper used in nixpkgs is not set up for it.
Fixing the wrapper would cause all of Darwin to rebuild, which is not
desirable, so just disable `-pipe` in the bootstrap configuration. The
clang integrated assembler doesn’t have the bug anyway.
The libgcc configure script was middetecting aarch64-darwin and trying
to use a deployment target of 10.5, which is not valid for that
platform. The build was failing because the linker was looking for stubs
that don’t exist (neither as part of the source releases nor as part of
the official SDK from Apple).
Backporting the `config.host` check and `t-darwin-rpath` from GCC 12
allows GCC 11 to build again on aarch64-darwin.
