testsuite: handle-multiline-outputs must allow both cc1 and cc1.exe

testsuite: handle-multiline-outputs must allow both cc1 and cc1.exe

Prior to 14-2027-g985d6480fe5, the input text had the file extensions
pruned. In 14-2027-g985d6480fe5, due to the move of the call, the
pruning is never done. This change restores the pruning of the file
extension to allow multiline test to pass on both Windows and other
platforms like Linux.

gcc/testsuite/ChangeLog:

	* lib/multiline.exp: Added pruning of .exe.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>