make
cc -I/usr/local/opt/ruby/include -c -o bestline.o bestline.c
In file included from bestline.c:122:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/termios.h:26:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:681:49: error: invalid token at start of a preprocessor expression
#if defined(_POSIX_C_SOURCE) && _POSIX_C_SOURCE == 1L
^