testbinary_is_stack_mte: declare main without extern "C"

The C++ standard doesn't allow a linkage-specification for main,
https://eel.is/c++draft/basic.start.main#3.sentence-5:

"The main function shall not be declared with a linkage-specification
([dcl.link])."

Bug: http://b/379133546
Test: treehugger
Change-Id: Ic864eaa6cc623c9344d05f9c7d18d090bc85715b

diff --git a/tests/libs/testbinary_is_stack_mte.cpp b/tests/libs/testbinary_is_stack_mte.cpp
index 0cdc466..3b6c79c 100644
--- a/tests/libs/testbinary_is_stack_mte.cpp
+++ b/tests/libs/testbinary_is_stack_mte.cpp
@@ -35,7 +35,7 @@
 
 #if defined(__BIONIC__) && defined(__aarch64__)
 
-extern "C" int main(int, char**) {
+int main(int, char**) {
   void* mte_tls_ptr = mte_tls();
   *reinterpret_cast<uintptr_t*>(mte_tls_ptr) = 1;
   int ret = is_stack_mte_on() && mte_tls_ptr != nullptr ? 0 : 1;
@@ -45,7 +45,7 @@
 
 #else
 
-extern "C" int main(int, char**) {
+int main(int, char**) {
   printf("RAN\n");
   return 1;
 }
diff --git a/tests/libs/testbinary_is_stack_mte_after_dlopen.cpp b/tests/libs/testbinary_is_stack_mte_after_dlopen.cpp
index 35af8f4..93b6670 100644
--- a/tests/libs/testbinary_is_stack_mte_after_dlopen.cpp
+++ b/tests/libs/testbinary_is_stack_mte_after_dlopen.cpp
@@ -84,7 +84,7 @@
   // Useless, but should defeat TCO.
   return new_low + fault_new_stack_page(low, f);
 }
-extern "C" int main(int argc, char** argv) {
+int main(int argc, char** argv) {
   if (argc < 2) {
     return 1;
   }
@@ -150,7 +150,7 @@
 }
 
 #else
-extern "C" int main(int, char**) {
+int main(int, char**) {
   return 1;
 }
 #endif