Mark __progname as weak for native_bridge

Bug: 167968941
Test: m
Change-Id: I636fab0bbf8e5565fb017940e6128c4bed3bab30
diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 01b6a42..80adbbe 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -58,6 +58,7 @@
 __LIBC_HIDDEN__ WriteProtected<libc_globals> __libc_globals;
 
 // Not public, but well-known in the BSDs.
+__BIONIC_WEAK_VARIABLE_FOR_NATIVE_BRIDGE
 const char* __progname;
 
 void __libc_init_globals() {