Fix portability failure introduced in commits d2b0b60 et al.

tglsfdc · tglsfdc · commit e9fcfed3fb6b · 2018-12-26T15:30:10.000-05:00
I made a frontend fprintf() format use %m, forgetting that that's only safe in HEAD not the back branches; prior to 96bf88d and d6c55de, it would work on glibc platforms but not elsewhere. Revert to using %s ... strerror(errno) as the code did before. We could have left HEAD as-is, but for code consistency across branches, I chose to apply this patch there too. Per Coverity and a few buildfarm members.
diff --git a/src/common/psprintf.c b/src/common/psprintf.c
@@ -115,7 +115,8 @@ pvsnprintf(char *buf, size_t len, const char *fmt, va_list args)
 #ifndef FRONTEND
 		elog(ERROR, "vsnprintf failed: %m with format string \"%s\"", fmt);
 #else
-		fprintf(stderr, "vsnprintf failed: %m with format string \"%s\"\n", fmt);
+		fprintf(stderr, "vsnprintf failed: %s with format string \"%s\"\n",
+				strerror(errno), fmt);
 		exit(EXIT_FAILURE);
 #endif
 	}
