qt5: fix build on gcc architectures

• the sed call was only replacing one of the %%LOCALBASE%% by ${LOCALBASE}, due to the missing 'g' flag to the sed call.

• with this change the gcc architectures should be able to build Qt5 again.

PR: 237745
Submitted by: Mark Millard <marklmi26-fbsd@yahoo.com>, jwb
Reported by: pkubaj