Compile with -fno-common
https://github.com/ggreer/the_silver_searcher/commit/21eaa1c4160b868b0c5bbf59da17974429f30055

Index: src/util.h
--- src/util.h.orig
+++ src/util.h
@@ -12,7 +12,7 @@
 #include "log.h"
 #include "options.h"
 
-FILE *out_fd;
+extern FILE *out_fd;
 
 #ifndef TRUE
 #define TRUE 1
@@ -51,7 +51,7 @@ typedef struct {
 } ag_stats;
 
 
-ag_stats stats;
+extern ag_stats stats;
 
 /* Union to translate between chars and words without violating strict aliasing */
 typedef union {
