Drop -flto

ccache saves us time on compiling, but not linking. The difference is unlikely to be significant for test purposes.

.travis.yml

@@ -12,7 +12,7 @@ env:
         - CCACHE_NOCPP2=true
         - CCACHE_SLOPPINESS=file_macro,time_macros,include_file_ctime,include_file_mtime
         - CCACHE_NOHASHDIR=true
-        - CFLAGS="-Ofast -pipe -fomit-frame-pointer -march=native -flto"
+        - CFLAGS="-Ofast -pipe -fomit-frame-pointer -march=native"
 
     matrix:
       # These are ordered to get as much diversity in the