Move compiler warning suppression for tests from cpp files to CMake

tests/assertion_tests.cpp

@@ -20,19 +20,6 @@
 #pragma warning(disable : 26440 26426) // from catch
 #endif
 
-#if __clang__ || __GNUC__
-//disable warnings from gtest
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wundef"
-#endif // __clang__ || __GNUC__
-
-#if __clang__
-#pragma GCC diagnostic ignored "-Wglobal-constructors"
-#pragma GCC diagnostic ignored "-Wused-but-marked-unused"
-#pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#pragma GCC diagnostic ignored "-Winconsistent-missing-destructor-override"
-#endif // __clang__
-
 #include <gtest/gtest.h>
 #include <gsl/gsl_assert> // for fail_fast (ptr only), Ensures, Expects
 
@@ -78,7 +65,3 @@ TEST(assertion_tests, ensures)
     EXPECT_TRUE(g(2) == 3);
     EXPECT_DEATH(g(9), deathstring);
 }
-
-#if __clang__ || __GNUC__
-#pragma GCC diagnostic pop
-#endif // __clang__ || __GNUC__