Have cl65 run the binaries from its own directory.

While ca65, cc65 and ld65 have built-in paths cl65 doesn't.
That means that up to now cl65 depended on the binaries
being found in the path env var. However it makes sense
to presume that the binaries are located in the very same
directory cl65 is located in. So whatever pathname was
suitable to run cl65 should be suitable to run the other
binaries too. But if for some reason there's no valid
argv[0] or if it doesn't contain at least one directory
delimiter ('/' or '\') then fall back to relying on the
path env var.

src/cl65/main.c

@@ -283,14 +283,22 @@ static void CmdAddFile (CmdDesc* Cmd, const char* File)
 
 
 
-static void CmdInit (CmdDesc* Cmd, const char* Path)
-/* Initialize the command using the given path to the executable */
+static void CmdInit (CmdDesc* Cmd, const char* Path, const char* Name)
+/* Initialize the command using the given path and name of the executable */
 {
+    char* FullName;
+
+    FullName = (char*) xmalloc (strlen (Path) + strlen (Name) + 1);
+    strcpy (FullName, Path);
+    strcat (FullName, Name);
+
     /* Remember the command */
-    Cmd->Name = xstrdup (Path);
+    Cmd->Name = xstrdup (FullName);
 
     /* Use the command name as first argument */
-    CmdAddArg (Cmd, Path);
+    CmdAddArg (Cmd, FullName);
+
+    xfree (FullName);
 }
 
 
@@ -1283,17 +1291,34 @@ int main (int argc, char* argv [])
 	{ "--zeropage-name",    1, 	OptZeropageName         },
     };
 
+    char* CmdPath;
     unsigned I;
 
     /* Initialize the cmdline module */
     InitCmdLine (&argc, &argv, "cl65");
 
     /* Initialize the command descriptors */
-    CmdInit (&CC65, "cc65");
-    CmdInit (&CA65, "ca65");
-    CmdInit (&CO65, "co65");
-    CmdInit (&LD65, "ld65");
-    CmdInit (&GRC,  "grc65");
+    if (argc == 0) {
+        CmdPath = xstrdup ("");
+    } else {
+        char* Ptr;
+        CmdPath = xstrdup (argv[0]);
+        Ptr = strrchr (CmdPath, '/');
+        if (Ptr == 0) {
+            Ptr = strrchr (CmdPath, '\\');
+        }
+        if (Ptr == 0) {
+            *CmdPath = '\0';
+        } else {
+            *(Ptr + 1) = '\0';
+        }
+    }
+    CmdInit (&CC65, CmdPath, "cc65");
+    CmdInit (&CA65, CmdPath, "ca65");
+    CmdInit (&CO65, CmdPath, "co65");
+    CmdInit (&LD65, CmdPath, "ld65");
+    CmdInit (&GRC,  CmdPath, "grc65");
+    xfree (CmdPath);
 
     /* Our default target is the C64 instead of "none" */
     Target = TGT_C64;