From /usr/include/stdin.h on Linux:

144 /* Standard streams.  */
145 extern struct _IO_FILE *stdin;      /* Standard input stream.  */
146 extern struct _IO_FILE *stdout;     /* Standard output stream.  */
147 extern struct _IO_FILE *stderr;     /* Standard error output stream.  */
148 /* C89/C99 say they're macros.  Make them happy.  */
149 #define stdin stdin
150 #define stdout stdout
151 #define stderr stderr

From /usr/include/stdin.h on Darwin:

    165 __BEGIN_DECLS
    166 #if __DARWIN_UNIX03
    167 extern FILE *__stdinp;
    168 extern FILE *__stdoutp;
    169 extern FILE *__stderrp;
    170 #else /* !__DARWIN_UNIX03 */
    171 extern FILE __sF[];
    172 #endif /* __DARWIN_UNIX03 */
    173 __END_DECLS
...

    235 #if __DARWIN_UNIX03
    236 #define stdin   __stdinp
    237 #define stdout  __stdoutp
    238 #define stderr  __stderrp
    239 #else /* !__DARWIN_UNIX03 */
    240 #define stdin   (&__sF[0])
    241 #define stdout  (&__sF[1])
    242 #define stderr  (&__sF[2])
    243 #endif /* __DARWIN_UNIX03 */

Hypothesis:  Could the '&' in lines 240-42 be the '&' about which 'make' is complaining when it hits src/embed/api.c?