forkfd: make only one of forkfd or spawnfd be compiled

We only ever use one, never both.

Change-Id: Iee8cbc07c4434ce9b560ffff13caf94c05dba338
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

src/3rdparty/forkfd/forkfd.c

@@ -436,6 +436,7 @@ static int create_pipe(int filedes[], int flags)
     return ret;
 }
 
+#ifndef FORKFD_NO_FORKFD
 /**
  * @brief forkfd returns a file descriptor representing a child process
  * @return a file descriptor, or -1 in case of failure
@@ -590,8 +591,9 @@ err_free:
     freeInfo(header, info);
     return -1;
 }
+#endif // FORKFD_NO_FORKFD
 
-#ifdef _POSIX_SPAWN
+#if defined(_POSIX_SPAWN) && !defined(FORKFD_NO_SPAWNFD)
 int spawnfd(int flags, pid_t *ppid, const char *path, const posix_spawn_file_actions_t *file_actions,
             posix_spawnattr_t *attrp, char *const argv[], char *const envp[])
 {
@@ -652,4 +654,4 @@ err_free:
 out:
     return -1;
 }
-#endif // _POSIX_SPAWN
+#endif // _POSIX_SPAWN && !FORKFD_NO_SPAWNFD

src/corelib/io/forkfd_qt.cpp

@@ -40,6 +40,13 @@
 #endif
 
 #include <QtCore/qatomic.h>
+#include "qprocess_p.h"
+
+#ifdef QPROCESS_USE_SPAWN
+#  define FORKFD_NO_FORKFD
+#else
+#  define FORKFD_NO_SPAWNFD
+#endif
 
 #if defined(QT_NO_DEBUG) && !defined(NDEBUG)
 #  define NDEBUG