compilers: avoid catching -Wl,-soname and wrapping with start/end group

This is just a bad regex match, because it matches *.so as a prospective
filename input even though it is actually not an input but a linker
flag. --start-group is only relevant to input files...

mesonbuild/compilers/mixins/clike.py

@@ -44,7 +44,7 @@ else:
     # do). This gives up DRYer type checking, with no runtime impact
     Compiler = object
 
-GROUP_FLAGS = re.compile(r'''\.so (?:\.[0-9]+)? (?:\.[0-9]+)? (?:\.[0-9]+)?$ |
+GROUP_FLAGS = re.compile(r'''^(?!-Wl,) .*\.so (?:\.[0-9]+)? (?:\.[0-9]+)? (?:\.[0-9]+)?$ |
                              ^(?:-Wl,)?-l |
                              \.a$''', re.X)