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/sys_sendfile_test.cpp b/tests/sys_sendfile_test.cpp
index 4cddd0d..1ec6c9f 100644
--- a/tests/sys_sendfile_test.cpp
+++ b/tests/sys_sendfile_test.cpp
@@ -43,7 +43,7 @@
   ASSERT_STREQ("ll", buf);
 }
 
-TEST(sys_sendfile, sendfile64) {
+TEST(sys_sendfile, sendfile64_smoke) {
   TemporaryFile src_file;
   ASSERT_EQ(5, TEMP_FAILURE_RETRY(write(src_file.fd, "hello", 5)));