tar: move vfork into separate function (smaller code)

open_transformer: more informative error messages

function                                             old     new   delta
vfork_compressor                                       -     210    +210
writeTarFile                                         547     299    -248
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 210/-248)          Total: -38 bytes

1 files changed, 5 insertions, 3 deletions

diff --git a/archival/libunarchive/open_transformer.c b/archival/libunarchive/open_transformer.c
index 3c551de06..8fb860234 100644
--- a/archival/libunarchive/open_transformer.c
+++ b/archival/libunarchive/open_transformer.c
@@ -22,11 +22,13 @@ int open_transformer(int src_fd,
 
 #if BB_MMU
         pid = fork();
+        if (pid == -1)
+                bb_perror_msg_and_die("can't fork");
 #else
         pid = vfork();
-#endif
         if (pid == -1)
-                bb_perror_msg_and_die("fork failed");
+                bb_perror_msg_and_die("can't vfork");
+#endif
 
         if (pid == 0) {
                 /* child process */
@@ -49,7 +51,7 @@ int open_transformer(int src_fd,
                         argv[2] = (char*)"-";
                         argv[3] = NULL;
                         BB_EXECVP(transform_prog, argv);
-                        bb_perror_msg_and_die("exec failed");
+                        bb_perror_msg_and_die("can't exec %s", transform_prog);
                 }
 #endif
                 /* notreached */