If @compiler isn't set/checked by ENV.compiler and the ENV.clang/etc.
methods, ENV.compiler may return unexpected results after fails_with
picks a fallback compiler.
See Homebrew/homebrew#22674.
This moves the CompilerSelector fails_with logic into the build
environment setup, making the compiler selection available before
performing actions that depends on knowing what the compiler is, e.g.
setting up PATH.
ENV.setup_build_environment now optionally takes a Formula argument
to provide the information necessary to do the fails_with, and the new
ENV.validate_cc! extracts the fails_with logic from Build.install.
ENV.compiler is called outside setting up the build environment, where
values unsupported for user input might have been specified - for
example, GNU GCC executables.
This unifies the logic for selecting a compiler between superenv and
stdenv. A variation of superenv's `determine_cc`, which now returns a
symbol, has been moved into the shared ENV extension. Stdenv uses the
result of this directly (as it's always used symbols), while superenv
translates that back into a compiler string.
This also has the effect of disabling HOMEBREW_USE_(gcc|llvm|clang) in
stdenv, which have already been marked as deprecated for some time, and
enables the HOMEBREW_CC= environment variable syntax from superenv in
stdenv.
On Unix, the path separator is ':', whereas on Windows,
it is ';'. This is the first of a series of patch to bring
macbrew's and winbrew's codebases closer together.
The main places the magic constant ':' was being used were:
- the $PATH environment variable
- CMAKE-related environment variables
- pkg-config related environment variables
ClosesHomebrew/homebrew#21921.
Signed-off-by: Jack Nagel <jacknagel@gmail.com>
