Building on macOS, where we *must* use an SDK, and there’s a choice of two: Xcode or Command Line Tools. The filesystem locations of the SDKs is different, but the effective content is the same.
I wish to support users who may have installed either (or both!) of the SDKs, without forcing them to specify which (e.g. via —sysroot=$XCODE or —sysroot=$CLT).
What I’ve come up with is this configure line:
--with-specs="%{!sysroot=*:--sysroot=%:if-exists-else($XCODE $CLT)}"
the idea of which is that if the user doesn’t specify —sysroot, the compiler will select XCODE if found, CLT if not.
If the user *does* specify —sysroot=foo, the compiler sees
COLLECT_GCC_OPTIONS='-v' \
'--sysroot=foo' \ <<<<<<<<<<<<<
'-mmacosx-version-min=15.0.0' \
'-asm_macosx_version_min=15.0' \
'-nodefaultexport' \
'-mcpu=apple-m1' \
'-mlittle-endian' \
'-mabi=lp64' \
'--sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk' \ <<<<<<<<<<< (CLT)
'-dumpdir' \
'a-'
which means that the —sysroot setting from the command line is overridden by the later setting derived from the —with-specs configure option.
How can I make it so that if the user *does* specify —sysroot, their choice prevents the compiler selecting the one derived from the —with-specs setting?
