Fix GCC 12 infinite loop in strlen

Strlen was jumping to strlen as part of -ftree-loop-distribute-patterns.
Seems this sort of issue can be common and generally fixed with
-fno-builtin. However, some of those optimizations may be useful and I
don't think our semantics for the functions are wildly different than
the standard, so I'm fixing this surgically with
-ftree-loop-distribute-patterns to just util.c. That may be the wrong
call, so if this bites us again, let's go more aggressive.

[Above is commit message from FlashFloppy, which also references
FlashFloppy GitHub issue 660.]

Refs #60

src/Makefile

@@ -14,3 +14,7 @@ OBJS += vectors.o
 
 .PHONY: build_info.c
 build_info.o: CFLAGS += -DFW_VER="\"$(FW_VER)\""
+
+# Avoid infinite loops due to GCC noticing code that can be replaced by a call
+# to a standard library function... within our implementation of that function.
+util.o: CFLAGS += -fno-tree-loop-distribute-patterns