posix_spawn-* tests: Fix test failure on mingw when libtool is in use

[Bruno Haible]

On mingw, when libtool is in use (such as in GNU gettext when --disable-shared
is not specified), 4 gnulib tests fail:
  test-posix_spawn-inherit0
  test-posix_spawn-inherit1
  test-posix_spawn-open1
  test-posix_spawn-open2

For example, test-posix_spawn-open1 fails with the error
  test-posix_spawn-open1:./.libs/lt-test-posix_spawn-open1.c:236: FATAL: 
couldn't find test-posix_spawn-open1.

In other words, the parent process successfully creates a child process that
executes test-posix_spawn-open1.exe (with an
argv[0] = "test-posix_spawn-open1").
That executable is the libtool wrapper. It uses
  find_executable (argv[0])
to locate the delegate executable. Given that argv[0], it does not find
.libs/test-posix_spawn-open1.exe. The fix is to make sure that argv[0] has
a ".exe" suffix. Thus, this patch fixes it. (Although it is debatable
whether that is a bug in the libtool wrapper's find_executable function.)


2022-09-14  Bruno Haible  <bruno@clisp.org>

        posix_spawn-* tests: Fix test failure on mingw when libtool is in use.
        * tests/test-posix_spawn-inherit0.c (CHILD_PROGRAM_FILENAME): Add the
        EXEEXT suffix.
        * tests/test-posix_spawn-inherit1.c (CHILD_PROGRAM_FILENAME): Likewise.
        * tests/test-posix_spawn-open1.c (CHILD_PROGRAM_FILENAME): Likewise.
        * tests/test-posix_spawn-open2.c (CHILD_PROGRAM_FILENAME): Likewise.

diff --git a/tests/test-posix_spawn-inherit0.c 
b/tests/test-posix_spawn-inherit0.c
index 4995ab7462..4e479233d9 100644
--- a/tests/test-posix_spawn-inherit0.c
+++ b/tests/test-posix_spawn-inherit0.c
@@ -31,7 +31,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#define CHILD_PROGRAM_FILENAME "test-posix_spawn-inherit0"
+#define CHILD_PROGRAM_FILENAME "test-posix_spawn-inherit0" EXEEXT
 #define DATA_FILENAME "test-posix_spawn-inh0-data.tmp"
 
 static int
diff --git a/tests/test-posix_spawn-inherit1.c 
b/tests/test-posix_spawn-inherit1.c
index 2e72a1a5a0..3308e30375 100644
--- a/tests/test-posix_spawn-inherit1.c
+++ b/tests/test-posix_spawn-inherit1.c
@@ -31,7 +31,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#define CHILD_PROGRAM_FILENAME "test-posix_spawn-inherit1"
+#define CHILD_PROGRAM_FILENAME "test-posix_spawn-inherit1" EXEEXT
 #define DATA_FILENAME "test-posix_spawn-inh1-data.tmp"
 
 static int
diff --git a/tests/test-posix_spawn-open1.c b/tests/test-posix_spawn-open1.c
index df4eb8917f..21e3cb4c05 100644
--- a/tests/test-posix_spawn-open1.c
+++ b/tests/test-posix_spawn-open1.c
@@ -37,7 +37,7 @@ SIGNATURE_CHECK (posix_spawn, int, (pid_t *, char const *,
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#define CHILD_PROGRAM_FILENAME "test-posix_spawn-open1"
+#define CHILD_PROGRAM_FILENAME "test-posix_spawn-open1" EXEEXT
 #define DATA_FILENAME "t!#$%&'()*+,-;=?@[\\]^_`{|}~.tmp"
 /* On Windows (including Cygwin), '*' '?' '\\' '|' cannot be used in file
    names.  */
diff --git a/tests/test-posix_spawn-open2.c b/tests/test-posix_spawn-open2.c
index 127d7a0b37..49ea5ed957 100644
--- a/tests/test-posix_spawn-open2.c
+++ b/tests/test-posix_spawn-open2.c
@@ -31,7 +31,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#define CHILD_PROGRAM_FILENAME "test-posix_spawn-open2"
+#define CHILD_PROGRAM_FILENAME "test-posix_spawn-open2" EXEEXT
 #define DATA_FILENAME "test-posix_spawn-open2-data.tmp"
 
 static int