mk: Don't build jemalloc with -g3

By default, jemalloc is building itself with -g3 if the local compiler supports
it. It looks like this is generating a good deal of debug info that windows
isn't optimizing out (on the order of 18MB). Windows gcc/ld is also not
optimizing this data away, causing hello world to be 18MB in size.

There's no current real need for debugging jemalloc to a great extent, so this
commit manually passes -g1 to override -g3 which jemalloc is using. This is
confirmed to drop the size of executables on windows back to a more reasonable
size (2.0MB, as they were before).

Closes #14144

mk/rt.mk

@@ -261,7 +261,7 @@ $$(JEMALLOC_LIB_$(1)): $$(JEMALLOC_DEPS) $$(MKFILE_DEPS)
 		AR="$$(AR_$(1))" \
 		RANLIB="$$(AR_$(1)) s" \
 		CPPFLAGS="-I $(S)src/rt/" \
-		EXTRA_CFLAGS="$$(CFG_CFLAGS_$(1))"
+		EXTRA_CFLAGS="$$(CFG_CFLAGS_$(1)) -g1"
 	$$(Q)$$(MAKE) -C "$$(JEMALLOC_BUILD_DIR_$(1))" build_lib_static
 	$$(Q)cp $$(JEMALLOC_BUILD_DIR_$(1))/lib/$$(JEMALLOC_REAL_NAME_$(1)) $$(JEMALLOC_LIB_$(1))