Description:
------------
php fails to build on macOS with Xcode 12. New in Xcode 12 is that implicitly declaring functions is now an error; before it was just a warning. Many of the configure script tests fail to include all of the required headers, leading to those tests failing to correctly identify the system's capabilities, such as:


conftest.c:103:5: error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
    exit(2);
    ^
conftest.c:103:5: note: include the header <stdlib.h> or explicitly provide a declaration for 'exit'
conftest.c:111:3: error: implicit declaration of function 'unlink' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  unlink(filename);
  ^


The build later fails, for example with this error:


main/reentrancy.c:125:23: error: too few arguments to function call, expected 3, have 2
        readdir_r(dirp, entry);
        ~~~~~~~~~            ^
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/dirent.h:110:1: note: 'readdir_r' declared here
int readdir_r(DIR *, struct dirent *, struct dirent **) __DARWIN_INODE64(readdir_r);
^


This was reported to MacPorts against php73 here: https://trac.macports.org/ticket/60988 and against php72 here: https://trac.macports.org/ticket/61168 but it also affects php74 and presumably all other php versions.