I found the dual use of CMAKE_*_PATH variables to make it difficult to
reason about this code. Now a separate set of variables are used to
communicate with the cc wrapper, and less work is performed in the
wrapper itself.
We no longer pass the SDK include path as a -isystem directory on
Xcode-only setups. Doing so is redundant with `--sysroot` and has other
side effects, namely changing the include path search order, which can
break compilation of some software (e.g. qemu).
On Xcode-only 10.9, we can additionally omit `--sysroot`, as the correct
paths are built into the tools.
A new variable, HOMEBREW_SYSROOT, is used to this information to the
wrapper. It will be unset on Xcode-only 10.9. HOMEBREW_SDKROOT will
continue to be set, as it is used for other things besides setting the
include search path.
On older Apple compilers "-O4" is known to cause build errors. On recent
clang, it's the same as "-O3" and you have to pass "-O3 -flto" to get
the old behavior.
It is activated by the same mechanism as the Homebrew/versions compilers
which now check if the GCC formula uses the same, correct version.
References Homebrew/homebrew#28418.
Rationale: our arg refurbishment is normally only turned on when
called via the `make` wrapper, for compatibility reasons. However,
there are numberous places we'd like this to be turned on elsewhere,
like software that builds via `python setup.py` where bad flags from
the system python can be pulled in.
This helper appends 'O' to CCCFG, which enables refurbishment for
all calls of the compiler shims.
This flag no longer affects the output of the compiler wrappers, since
everything is buffered by the build process rather than each individual
tool.
Additionally, this is a user-facing knob that affects ARGV.verbose?, and
the combination of these two issues broke the --quieter feature.
The mapping of architectures to optimization flags is now retrieved from
Hardware::CPU and the selected flags are passed as an environmen
variable, rather than duplicated in the cc wrapper and re-calculated on
every invocation of the compiler.
ClosesHomebrew/homebrew#24540.
Constructing the path relative to a file in the repository is incorrect
on some supported configurations (i.e., the repository is located in a
different place than the prefix).
ClosesHomebrew/homebrew#24418.
