Revert "[sanitizer_common][test-only] Specify full path for sort executable in popen.cpp" (#171706)

Reverts #171622

Co-authored-by: Andrew Haberlandt <ndrewh@users.noreply.github.com>

Author: DanBlackwell

compiler-rt/test/sanitizer_common/TestCases/Posix/popen.cpp

@@ -8,7 +8,7 @@
 int main(void) {
   // use a tool that produces different output than input to verify
   // that everything worked correctly
-  FILE *fp = popen("/usr/bin/sort", "w");
+  FILE *fp = popen("sort", "w");
   assert(fp);
 
   // verify that fileno() returns a meaningful descriptor (needed