The libqt5-qtscript package fails to build on PowerPC, since it attempts
to force building the JIT, which is not supported on PowerPC.

This is done by the build scripts because the file
/usr/lib64/qt5/mkspecs/qmodule.pri
contains the entry
JAVASCRIPTCORE_JIT = yes

That file in turn is created by this package, libqt5-qtbase, which sets
the JAVASCRIPTCORE_JIT entry because configure is called with the
-javascript-jit option.

This doesn't seem useful for platforms where the JIT is not supported,
so this patch removes the option for PowerPC.

- Do not force -javascript-jit on ppc platforms that do not support it. (forwarded request 211854 from uweigand)