win32: code shrink detection of executables

Add a function, file_is_win32_exe(), to detect if a path refers
to an executable.  It tries adding extensions if necessary.

Use this in a number of places to replace common code of the form

   path = alloc_ext_space(cmd);
   if (add_win32_extension(path) || file_is_executable(path))

Saves 32-48 bytes.

1 files changed, 6 insertions, 4 deletions

diff --git a/libbb/executable.c b/libbb/executable.c
index 770aedc0c..606bec986 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -57,10 +57,12 @@ char* FAST_FUNC find_executable(const char *filename, char **PATHp)
                 );
 #if ENABLE_PLATFORM_MINGW32
                 {
-                        char *w = alloc_ext_space(p);
-                        ex = add_win32_extension(w) || file_is_executable(w);
-                        free(p);
-                        p = w;
+                        char *w = file_is_win32_exe(p);
+                        ex = w != NULL;
+                        if (ex) {
+                                free(p);
+                                p = w;
+                        }
                 }
 #else
                 ex = file_is_executable(p);