Switch to g_ for globals.

That's what the Google style guide recommends, and we're starting
to get a mix.

Change-Id: Ib0c53a890bb5deed5c679e887541a715faea91fc
diff --git a/linker/linker_debug.h b/linker/linker_debug.h
index 7a5821a..3faa38e 100644
--- a/linker/linker_debug.h
+++ b/linker/linker_debug.h
@@ -55,17 +55,17 @@
 
 #include "private/libc_logging.h"
 
-__LIBC_HIDDEN__ extern int gLdDebugVerbosity;
+__LIBC_HIDDEN__ extern int g_ld_debug_verbosity;
 
 #if LINKER_DEBUG_TO_LOG
 #define _PRINTVF(v, x...) \
     do { \
-      if (gLdDebugVerbosity > (v)) __libc_format_log(5-(v), "linker", x); \
+      if (g_ld_debug_verbosity > (v)) __libc_format_log(5-(v), "linker", x); \
     } while (0)
 #else /* !LINKER_DEBUG_TO_LOG */
 #define _PRINTVF(v, x...) \
     do { \
-      if (gLdDebugVerbosity > (v)) { __libc_format_fd(1, x); write(1, "\n", 1); } \
+      if (g_ld_debug_verbosity > (v)) { __libc_format_fd(1, x); write(1, "\n", 1); } \
     } while (0)
 #endif /* !LINKER_DEBUG_TO_LOG */