selftests/nolibc: only run constructor tests on nolibc

The nolibc testsuite can be run against other libcs to test for
interoperability. Some aspects of the constructor execution are not
standardized and musl does not provide all tested feature, for one it
does not provide arguments to the constructors, anymore?

Skip the constructor tests on non-nolibc configurations.

Acked-by: Willy Tarreau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Thomas Weißschuh <[e-mail]>

tools/testing/selftests/nolibc/nolibc-test.c

···
 		CASE_TEST(environ_HOME);     EXPECT_PTRNZ(1, getenv("HOME")); break;
 		CASE_TEST(auxv_addr);        EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
 		CASE_TEST(auxv_AT_UID);      EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
-		CASE_TEST(constructor);      EXPECT_EQ(1, constructor_test_value, 2); break;
+		CASE_TEST(constructor);      EXPECT_EQ(is_nolibc, constructor_test_value, 2); break;
 		CASE_TEST(linkage_errno);    EXPECT_PTREQ(1, linkage_test_errno_addr(), &errno); break;
-		CASE_TEST(linkage_constr);   EXPECT_EQ(1, linkage_test_constructor_test_value, 6); break;
+		CASE_TEST(linkage_constr);   EXPECT_EQ(is_nolibc, linkage_test_constructor_test_value, 6); break;
 		case __LINE__:
 			return ret; /* must be last */
 		/* note: do not set any defaults so as to permit holes above */