remove forced gcc optimization
remove forced gcc optimization

It was added in 6d6bd8ba78434ecb09395582b5f3e41febd4d4ee,
but it is unclear for me, why this is needed or if it is
required. I don't think we should depend on some gcc
optimization, which might change in the future.
Anyway, this breaks c6x toolchain building (ICE), so I remove it.
Testsuite run for supported architectures didn't add any
new errors.

kraj/uclibc-ng,kraj/uclibc-ng,wbx-github/uclibc-ng,brgl/uclibc-ng,wbx-github/uclibc-ng,wbx-github/uclibc-ng,kraj/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,foss-for-synopsys-dwc-arc-processors/uClibc,kraj/uclibc-ng,foss-for-synopsys-dwc-arc-processors/uClibc,brgl/uclibc-ng,brgl/uclibc-ng,brgl/uclibc-ng,wbx-github/uclibc-ng