libbb: fix regression where 'which' output duplicate slashes

If an element of $PATH had a trailing slash 'which' displayed two
slashes when an executable was found in that directory.

This is a regression caused by upstream commit 49d9e06fb (libbb:
modify find_executable() to not temporarily write to PATH).
Prior to this commit find_executable() used concat_path_file() to
build the path of the executable.  This avoids including duplicate
slashes in its output.  The new code didn't.

Add a test in find_executable() to detect the problem.  It still
fails if there are multiple trailing slashes.  Don't do that.

Adds 48 bytes.

1 files changed, 8 insertions, 0 deletions

diff --git a/libbb/executable.c b/libbb/executable.c
index 263141912..57969033c 100644
--- a/libbb/executable.c
+++ b/libbb/executable.c
@@ -50,6 +50,14 @@ char* FAST_FUNC find_executable(const char *name, const char **PATHp)
                 int ex;
 
                 if (sz != 0) {
+#if ENABLE_PLATFORM_MINGW32
+                        // Strip trailing slash from path
+                        if (is_dir_sep(end[-1]))
+                                --sz;
+                        if (sz == 0)    // "/" in PATH, unlikely but not impossible
+                                p = xasprintf("%.*s/%s" + 4, name);
+                        else
+#endif
                         p = xasprintf("%.*s/%s", sz, p, name);
                 } else {
                         /* We have xxx::yyy in $PATH,