Ticket #61827: mkmf.log

"/usr/bin/clang -o conftest -I/opt/local/include/ruby-2.7.0/x86_64-darwin20 -I/opt/local/include/ruby-2.7.0/ruby/backward -I/opt/local/include/ruby-2.7.0 -I. -I/opt/local/include -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk -I/opt/local/include -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT   -pipe -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk -fno-common  -I /opt/local/include/libxml2 conftest.c  -L. -L/opt/local/lib -L/opt/local/lib -L. -L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-syslibroot,/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk -fstack-protector-strong -L/opt/local/lib   -arch x86_64   -lruby.2.7    "
clang: warning: no such sysroot directory: '/Library/Developer/CommandLineTools/SDKs/MacOSX11.0.sdk' [-Wmissing-sysroot]
In file included from conftest.c:1:
In file included from /opt/local/include/ruby-2.7.0/ruby.h:33:
In file included from /opt/local/include/ruby-2.7.0/ruby/ruby.h:29:
/opt/local/include/ruby-2.7.0/ruby/defines.h:126:10: fatal error: 'stdio.h' file not found
#include <stdio.h>
         ^~~~~~~~~
1 error generated.
checked program was:
/* begin */
1: #include "ruby.h"
2: 
3: int main(int argc, char **argv)
4: {
5:   return !!argv[argc];
6: }
/* end */