Build bionic unit tests for musl

Modify bionic unit tests that are built for glibc so that they also
build against musl.  They don't all pass though:

With glibc:
 2 SLOW TESTS
 4 TIMEOUT TESTS
313 FAILED TESTS
  YOU HAVE 2 DISABLED TESTS

With musl:
11 SLOW TESTS
11 TIMEOUT TESTS
363 FAILED TESTS
  YOU HAVE 2 DISABLED TESTS

Bug: 190084016
Test: m bionic-unit-tests-glibc with musl
Test: atest bionic-unit-tests-static
Test: atest --host bionic-unit-tests-glibc with glibc
Change-Id: I79b6eab04fed3cc4392450df5eef2579412edfe1
diff --git a/tests/netinet_in_test.cpp b/tests/netinet_in_test.cpp
index 437e180..8343f57 100644
--- a/tests/netinet_in_test.cpp
+++ b/tests/netinet_in_test.cpp
@@ -31,6 +31,7 @@
 static constexpr uint64_t be64 = 0xf0debc9a78563412;
 
 TEST(netinet_in, bindresvport) {
+#if !defined(MUSL)
   // This isn't something we can usually test (because you need to be root),
   // so just check the symbol's there.
   ASSERT_EQ(-1, bindresvport(-1, nullptr));
@@ -40,6 +41,9 @@
   errno = 0;
   ASSERT_EQ(-1, bindresvport(-1, &sin));
   ASSERT_EQ(EPFNOSUPPORT, errno);
+#else
+  GTEST_SKIP() << "musl doesn't support bindresvport";
+#endif
 }
 
 TEST(netinet_in, in6addr_any) {