Revert "Revert "Fix dlsym() to take into account RTLD_GLOBAL/LOCAL""

This reverts commit 9d3382d97a2cdc8c8f78c7825ece16f09292fc36.
diff --git a/tests/libs/dlopen_testlib_simple.cpp b/tests/libs/dlopen_testlib_simple.cpp
index bf750b2..3226955 100644
--- a/tests/libs/dlopen_testlib_simple.cpp
+++ b/tests/libs/dlopen_testlib_simple.cpp
@@ -19,6 +19,6 @@
 
 uint32_t dlopen_testlib_taxicab_number = 1729;
 
-bool dlopen_testlib_simple_func() {
+extern "C" bool dlopen_testlib_simple_func() {
   return true;
 }