fix: typo and err handle in build script

scripts/WIN/cppBuilds.bat

@@ -3,13 +3,14 @@ echo --- start cppBuilds.bat ---
 echo --- prebuild ---
 set workDir=%__CD__%
 echo working directory: %workDir%
-IF "$1"=="clean" (
+IF "%1"=="clean" (
     echo --- clean build directory ---
     IF exist %workDir%cpp\build\ (
         rmdir /s /q %workDir%cpp\build
     ) ELSE (
         echo warning: build directory not found
     )
+    cd %workDir%
     exit /b 0
 )
 
@@ -28,24 +29,25 @@ IF "%2"=="mingw" (
 )
 
 IF errorlevel 1 (
-    echo Error: cmake failed
+    echo Error: cmake initation failed
+    cd %workDir%
     exit /b 1
 )
 
 IF "%1"=="multi" (
-    set targetName="MiraiCP_multi"
+    set targetName=MiraiCP_multi
     goto build
 )
 IF "%1"=="single" (
-    set targetName="MiraiCP_single"
+    set targetName=MiraiCP_single
     goto build
 )
 IF "%1"=="libLoader" (
-    set targetName="Loader"
+    set targetName=Loader
     goto build
 )
 IF "%1"=="libLoaderNative" (
-    set targetName="LoaderNative"
+    set targetName=LoaderNative
     goto build
 )
 
@@ -60,6 +62,12 @@ cd %workDir%cpp
 cmake --build build --target %targetName% --config Release
 @echo off
 
+IF errorlevel 1 (
+    echo Error: %targetName% build failed
+    cd %workDir%
+    exit /b 1
+)
+
 :end
 echo --- end cppBuilds.bat ---
 :: restore working directory