Fix x86 system calls made from ELF preinit.

Used by CFI, so broke cfi_test#early_init@x86, but I've added a specific
test for this (and a similar test for getauxval from preinit, which this
patch does not fix).

Bug: http://b/35885875
Test: ran tests
Change-Id: I43885bedfb88c0a26b4474bd3c27a87dec7bbc97
diff --git a/tests/libs/Android.bp b/tests/libs/Android.bp
index 5eb16c5..a031fe9 100644
--- a/tests/libs/Android.bp
+++ b/tests/libs/Android.bp
@@ -547,3 +547,17 @@
     shared_libs: ["libcfi-test"],
     ldflags: ["-Wl,--rpath,${ORIGIN}/.."],
 }
+
+cc_test {
+    name: "preinit_getauxval_test_helper",
+    host_supported: false,
+    defaults: ["bionic_testlib_defaults"],
+    srcs: ["preinit_getauxval_test_helper.cpp"],
+}
+
+cc_test {
+    name: "preinit_syscall_test_helper",
+    host_supported: false,
+    defaults: ["bionic_testlib_defaults"],
+    srcs: ["preinit_syscall_test_helper.cpp"],
+}