posix: add $VLC_LIBEXEC_PATH

We already track $pkglibexecdir separately from $pkglibdir when VLC is
installed. This adds it in the build tree.

bin/vlc.c

@@ -143,6 +143,7 @@ int main(int argc, const char *argv[])
     setenv ("VLC_PLUGIN_PATH", TOP_BUILDDIR"/modules", 1);
     setenv ("VLC_DATA_PATH", TOP_SRCDIR"/share", 1);
     setenv ("VLC_LIB_PATH", TOP_BUILDDIR"/modules", 1);
+    setenv ("VLC_LIBEXEC_PATH", TOP_BUILDDIR"/modules", 1);
 #endif
 
     /* Clear the X.Org startup notification ID. Otherwise the UI might try to

src/posix/dirs.c

@@ -50,7 +50,7 @@ char *config_GetSysPath(vlc_sysdir_t type, const char *filename)
     static const char env_vars[][16] = {
         [VLC_PKG_DATA_DIR] = "VLC_DATA_PATH",
         [VLC_PKG_LIB_DIR] = "VLC_LIB_PATH",
-        [VLC_PKG_LIBEXEC_DIR] = "VLC_LIB_PATH",
+        [VLC_PKG_LIBEXEC_DIR] = "VLC_LIBEXEC_PATH",
     };
 
     if (type < ARRAY_SIZE(env_vars)) {