php8: add patch for loongarch64 support

php8: add patch for loongarch64 support

This backported patch is required to fix the build for loongarch64:
...
... loongarch64-openwrt-linux-musl/bin/ld.bfd: Zend/zend_fibers.o: in function `zend_fiber_init_context':
zend_fibers.c:(.text+0xb34): undefined reference to `getcontext'
... loongarch64-openwrt-linux-musl/bin/ld.bfd: zend_fibers.c:(.text+0xb38): undefined reference to `getcontext'
... loongarch64-openwrt-linux-musl/bin/ld.bfd: zend_fibers.c:(.text+0xb74): undefined reference to `makecontext'
... loongarch64-openwrt-linux-musl/bin/ld.bfd: zend_fibers.c:(.text+0xb78): undefined reference to `makecontext'
... loongarch64-openwrt-linux-musl/bin/ld.bfd: Zend/zend_fibers.o: in function `.L170':
zend_fibers.c:(.text+0xe34): undefined reference to `swapcontext'
...

Signed-off-by: Michael Heimpold <mhei@heimpold.de>