[libc] lfind_test.cpp: put helpers in an anonymous namespace. (llvm#137821)

This matches other tests and allows the tests to be built together (as
Android is doing).

Author: enh-google

libc/test/src/search/lfind_test.cpp

@@ -9,10 +9,14 @@
 #include "src/search/lfind.h"
 #include "test/UnitTest/Test.h"
 
+namespace {
+
 int compar(const void *a, const void *b) {
   return *reinterpret_cast<const int *>(a) != *reinterpret_cast<const int *>(b);
 }
 
+} // namespace
+
 TEST(LlvmLibcLfindTest, SearchHead) {
   int list[3] = {1, 2, 3};
   size_t len = 3;