include headers only if the related option is enabled

libc/pwd_grp/pwd_grp.c

@@ -41,7 +41,10 @@
 #include <ctype.h>
 #include <pwd.h>
 #include <grp.h>
+#include <paths.h>
+#ifdef __HAS_SHADOW__
 #include <shadow.h>
+#endif
 #ifdef __UCLIBC_HAS_THREADS__
 #include <pthread.h>
 #endif

libc/unistd/getopt.c

@@ -26,10 +26,13 @@
  * Modified once again for uClibc by Erik Andersen 8/7/02
  */
 
+#include <features.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
+#ifdef __UCLIBC_HAS_GETTEXT_AWARENESS__
 #include <libintl.h>
+#endif
 
 #ifdef __UCLIBC_MJN3_ONLY__
 #warning TODO: Enable gettext awareness.

libc/unistd/sysconf.c

@@ -29,7 +29,9 @@
 #include <unistd.h>
 #include <sys/sysinfo.h>
 #include <sys/types.h>
+#ifdef __UCLIBC_HAS_REGEX__
 #include <regex.h>
+#endif
 
 #ifndef __UCLIBC_CLK_TCK_CONST
 #error __UCLIBC_CLK_TCK_CONST not defined!

librt/kernel-posix-timers.h

@@ -2,10 +2,13 @@
  * kernel-posix-timers.h - kernel-dependent definitions for POSIX timers.
  */
 
+#include <features.h>
 #include <setjmp.h>
 #include <signal.h>
 #include <sys/types.h>
+#ifdef __UCLIBC_HAS_THREADS__
 #include <pthread.h>
+#endif
 
 /* Type of timers in the kernel */
 typedef int kernel_timer_t;
@@ -27,5 +30,7 @@ struct timer {
     /* Parameters for the thread to be started for SIGEV_THREAD */
     void (*thrfunc) (sigval_t);
     sigval_t sival;
+#ifdef __UCLIBC_HAS_THREADS__
     pthread_attr_t attr;
+#endif
 };