[lld-macho] Enable search-paths tests on macOS

I'm not sure what the history is here but this test passes on macOS
today. It seems like we should unify these tests if they need to run
cross platform.

Reviewed By: #lld-macho, int3

Differential Revision: https://reviews.llvm.org/D113085

lld/test/MachO/search-paths.test

@@ -1,6 +1,4 @@
-UNSUPPORTED: darwin
-
-RUN: mkdir -p %t1 %t2
+RUN: rm -rf %t1 %t2; mkdir -p %t1 %t2
 
 RUN: %lld -v -dylib -o /dev/null -L%t1 -F%t2 2>&1 \
 RUN:     | FileCheck -DLDIR=%t1 -DFDIR=%t2 %s