fix(gcc): add -fPIC to mimalloc compilation

Wasn't needed on clang, but is needed with gcc:

    /usr/bin/ld: mimalloc-override.o: relocation R_X86_64_TPOFF32
    against `recurse' can not be used when making a shared object;
    recompile with -fPIC

lua/wincent/commandt/lib/Makefile

@@ -71,7 +71,7 @@ $(eval $(call DEPEND_ON,CCFLAGS))
 $(eval $(call DEPEND_ON,USE_MIMALLOC))
 
 $(MIMALLOC_OVERRIDE): $(MIMALLOC_HDRS) $(MIMALLOC_SRCS) Makefile .make/CCFLAGS
-	$(CC) $(CCFLAGS) -I$(MIMALLOC_INCLUDE) -c -o $(MIMALLOC_OVERRIDE) $(MIMALLOC_SRC)/static.c
+	$(CC) $(CCFLAGS) -I$(MIMALLOC_INCLUDE) -c -fPIC -o $(MIMALLOC_OVERRIDE) $(MIMALLOC_SRC)/static.c
 
 commandt.$(DLLEXT): $(HDRS) $(SRCS) $(MIMALLOC_OVERRIDE) Makefile .make/CCFLAGS .make/USE_MIMALLOC
 	$(CC) $(CCFLAGS) -shared -fPIC -o commandt.$(DLLEXT) $(MALLOC_OBJ) $(SRCS)