posix_spawn: fix get/set uid/gid calls for 32 bit Cygwin

32 bit Cygwin still exports function calls to support old applications.
E. g., when switching from 16 to 32 bit uid/gid values, new function
like getuid32 have been added and the old getuid function still only
provides 16 bit values.  Newly built applications using getuid are
actually calling getuid32.

However, this link magic isn't performed inside Cygwin itself, so if
newlib functions call getuid, they actually call the old getuid, not
the new getuid32.  This leads to truncated uid/gid values.

https://cygwin.com/pipermail/cygwin/2022-January/250453.html reports
how this leads to problems in posix_spawn.

Fix this temporarily. i686 support will go away soon in Cygwin and the
fix can be dropped.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

newlib/libc/posix/posix_spawn.c

@@ -146,6 +146,17 @@ typedef struct __posix_spawn_file_actions_entry {
  * Spawn routines
  */
 
+#if defined (__CYGWIN__) && defined (__i386__)
+extern int getgid32 (void);
+extern int getuid32 (void);
+extern int setegid32 (gid_t egid);
+extern int seteuid32 (uid_t euid);
+#define setegid setegid32
+#define seteuid seteuid32
+#define getgid getgid32
+#define getuid getuid32
+#endif
+
 static int
 process_spawnattr(const posix_spawnattr_t sa)
 {

winsup/cygwin/release/3.3.4

@@ -20,3 +20,6 @@ Bug Fixes
 
 - Ignore INHERIT ACEs when reading the DACL of non-directory files.
   Addresses: https://cygwin.com/pipermail/cygwin/2022-January/250363.html
+
+- Fix an "Invalid argument" problem in posix_spawn on i686.
+  Addresses: https://cygwin.com/pipermail/cygwin/2022-January/250453.html