update openwrt Makefile

[shalzz]

This disables compiling with -O2 flag since it breaks cross-compiling with at least the MIPS architecture.

Optimizations should be safe to re-enable when the build is fixed to handle COPTS compile flags correctly.

[pinheadmz]

Awesome, thanks so much for this contribution. If possible, can you explain how I could reproduce the issue? (like, do you own a MIPS device or something?). It would be nice of course to keep optimizations even if it means more work to fix the build.

[shalzz]

Awesome, thanks so much for this contribution. If possible, can you explain how I could reproduce the issue? (like, do you own a MIPS device or something?). It would be nice of course to keep optimizations even if it means more work to fix the build.

Yes, I'm build this for a MIPS device when I encounter this issue.
You can reproduce by having at least these in your .config file when building openwrt.

CONFIG_TARGET_ath79=y
CONFIG_TARGET_ath79_generic=y
CONFIG_TARGET_ath79_generic_DEVICE_tplink_archer-a7-v5=y