fix: pcmake output 后缀处理

- output = demo  -> demo.exe (自动追加 .exe)
- output = demo.exe -> demo.exe (不重复追加)
- output = demo.EXE -> demo.EXE (大小写不敏感)
- clean 命令同步修复

tools/pcmake.c

@@ -190,6 +190,29 @@ static int file_exists(const char *f) {
     return 0;
 }
 
+/* build the output file name: append .exe on Windows only if
+   the configured name does not already end with .exe (case-insensitive) */
+static int ends_with_exe(const char *s)
+{
+    int n = (int)strlen(s);
+    if (n < 4) return 0;
+    s += n - 4;
+    return (tolower((unsigned char)s[1])=='e')
+        && (tolower((unsigned char)s[2])=='x') && (tolower((unsigned char)s[3])=='e');
+}
+
+static void make_output_name(const char *in, char *out, int outsize)
+{
+    int n = (int)strlen(in);
+    if (n >= outsize) n = outsize - 1;
+    memcpy(out, in, n);
+    out[n] = 0;
+#ifdef _WIN32
+    if (!ends_with_exe(out))
+        strncat(out, ".exe", outsize - n - 1);
+#endif
+}
+
 /* run a command line; Windows uses CreateProcess to handle
    quoted paths with spaces correctly (system() misbehaves) */
 static int run_command(const char *cmd) {
@@ -275,11 +298,7 @@ int main(int argc, char **argv) {
         }
         {
             char outbuf[512];
-            strncpy(outbuf, g_output, sizeof outbuf - 1);
-            outbuf[sizeof outbuf - 1] = 0;
-#ifdef _WIN32
-            strncat(outbuf, ".exe", sizeof outbuf - strlen(outbuf) - 1);
-#endif
+            make_output_name(g_output, outbuf, sizeof outbuf);
             printf("  rm %s\n", outbuf);
             remove(outbuf);
         }
@@ -323,11 +342,7 @@ int main(int argc, char **argv) {
         len += snprintf(cmd + len, sizeof cmd - len, " -l%s", g_libs[i]);
     {
         char outbuf[512];
-        strncpy(outbuf, g_output, sizeof outbuf - 1);
-        outbuf[sizeof outbuf - 1] = 0;
-#ifdef _WIN32
-        strncat(outbuf, ".exe", sizeof outbuf - strlen(outbuf) - 1);
-#endif
+        make_output_name(g_output, outbuf, sizeof outbuf);
         len += snprintf(cmd + len, sizeof cmd - len, " -o \"%s\"", outbuf);
     }
     printf("  link %s\n", g_output);
@@ -337,12 +352,10 @@ int main(int argc, char **argv) {
         return 1;
     }
 
-    printf("pcmake: build OK -> %s%s\n", g_output,
-#ifdef _WIN32
-           ".exe"
-#else
-           ""
-#endif
-    );
+    {
+        char outbuf[512];
+        make_output_name(g_output, outbuf, sizeof outbuf);
+        printf("pcmake: build OK -> %s\n", outbuf);
+    }
     return 0;
 }