mkspecs: Allow specifying a CROSS_COMPILE for mac/clang targets

This allows distinguishing between these tools and tools for the host,
when cross compiling.

While mac tools normally only are available on macOS, there are third
party efforts to port them to other platforms. In these cases, it
might be useful to use a prefix (either some sort of triplet prefix,
or an absolute path) to distinguish between the host build platform
compilers/tools and the ones for the cross target.

The use of this variable matches the one used in a lot of other
mkspecs, and shouldn't cause any issues for those who aren't setting
it.

Change-Id: Iaeba571d955ea79ed1249989fcc525eb1eaf1f5c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

0 files changed, 0 insertions, 0 deletions