got linking on OS X working, tested on a Pi too. lets see about travis.

Makefile

@@ -71,6 +71,7 @@ test_prelim:
 	${PYTHON} --version
 	${PYTHON} -c 'import greenlet; print(greenlet, greenlet.__version__)'
 	${PYTHON} -c 'import gevent.core; print(gevent.core.loop)'
+	${PYTHON} -c 'import gevent.libuv.corecffi; print(dir(gevent.libuv.corecffi.libuv))'
 	make bench
 
 toxtest: test_prelim

_setuplibuv.py

@@ -119,6 +119,13 @@ def configure_libuv(_bext, _ext):
         cflags = '-fPIC'
         env = os.environ.copy()
         env['CFLAGS'] = ' '.join(x for x in (cflags, env.get('CFLAGS', None), env.get('ARCHFLAGS', None)) if x)
+        # Since we're building a static library, if link-time-optimization is requested, it
+        # results in failure to properly create the library archive. This goes unnoticed on
+        # OS X until import time because of '-undefined dynamic_lookup'. On the raspberry
+        # pi, it causes the linker to crash
+        if '-flto' in env['CFLAGS']:
+            log.info("Removing LTO")
+            env['CFLAGS'] = env['CFLAGS'].replace('-flto', '')
         log.info('Building libuv...')
         if WIN:
             prepare_windows_env(env)