[Ada] Do not expect execv to return 0

[Ada] Do not expect execv to return 0

[Pierre-Marie de Rodat]

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When spawning subprocesses with fork & execv there is no need to check
the result of execve, because it either succeeds and does not return or
fails and returns -1.

This is only a code cleanup related to the use of fork-vs-vfork in
GNATprove; behaviour is unaffected, though the GNAT runtime library
will be marginally smaller.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* adaint.c (__gnat_portable_spawn): Do not expect execv to
	return 0.
	(__gnat_portable_no_block_spawn): Likewise.

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diff --git a/gcc/ada/adaint.c b/gcc/ada/adaint.c
--- a/gcc/ada/adaint.c
+++ b/gcc/ada/adaint.c
@@ -2424,8 +2424,10 @@ __gnat_portable_spawn (char *args[] ATTRIBUTE_UNUSED)
   if (pid == 0)
     {
       /* The child. */
-      if (execv (args[0], MAYBE_TO_PTR32 (args)) != 0)
-	_exit (1);
+      execv (args[0], MAYBE_TO_PTR32 (args));
+
+      /* execv() returns only on error */
+      _exit (1);
     }
 
   /* The parent.  */
@@ -2822,8 +2824,10 @@ __gnat_portable_no_block_spawn (char *args[] ATTRIBUTE_UNUSED)
   if (pid == 0)
     {
       /* The child.  */
-      if (execv (args[0], MAYBE_TO_PTR32 (args)) != 0)
-	_exit (1);
+      execv (args[0], MAYBE_TO_PTR32 (args));
+
+      /* execv() returns only on error */
+      _exit (1);
     }
 
   return pid;