Move VS dev command prompt call to re_write_il.cmd

Technically, this only needs to be run when specifically running this script.

build.cmd

@@ -1,17 +1,3 @@
 @echo off
 setlocal
-
-:: Invoke VS Developer Command Prompt batch file.
-:: This sets up some environment variables needed to use ILDasm and ILAsm.
-if not defined VisualStudioVersion (
-    if defined VS140COMNTOOLS (
-        call "%VS140COMNTOOLS%\VsDevCmd.bat"
-        goto :Build
-    )
-
-    echo Error: build.cmd requires Visual Studio 2015.
-    exit /b 1
-)
-
-:Build
 powershell -NoProfile %~dp0scripts\build.ps1 %*

package.cmd

@@ -1,17 +1,3 @@
 @echo off
 setlocal
-
-:: Invoke VS Developer Command Prompt batch file.
-:: This sets up some environment variables needed to use ILDasm and ILAsm.
-if not defined VisualStudioVersion (
-    if defined VS140COMNTOOLS (
-        call "%VS140COMNTOOLS%\VsDevCmd.bat"
-        goto :Package
-    )
-
-    echo Error: package.cmd requires Visual Studio 2015.
-    exit /b 1
-)
-
-:Package
 powershell -NoProfile %~dp0scripts\package.ps1 %*

src/System.Slices/re_write_il.cmd

@@ -1,3 +1,20 @@
+@echo off
+setlocal
+
+:: Invoke VS Developer Command Prompt batch file.
+:: This sets up some environment variables needed to use ILDasm and ILAsm.
+if not defined VisualStudioVersion (
+    if defined VS140COMNTOOLS (
+        call "%VS140COMNTOOLS%\VsDevCmd.bat"
+        goto :Rewrite
+    )
+
+    echo Error: re_write_il.cmd requires Visual Studio 2015.
+    exit /b 1
+)
+
+:Rewrite
+@echo on
 tools\ildasm.exe /caverbal /linenum /out:%1\system.slices.beforerewrite.il /nobar %2
 tools\ILSub\ILSub.exe %1\system.slices.beforerewrite.il %1\system.slices.rewritten.il
 tools\ilasm.exe /quiet /pdb /dll /out:%2 /nologo %1\system.slices.rewritten.il