make.bat: fix compare between GOROOT and srcdir paths, when either contains whitespace.

CL 96455 brings CL 57753 to Windows
However, a path comparison within it was left unquoted.
If the Go source directory resides in a path containing whitespace,
the interpreter will compare against the first portion of the path string,
and treat the remainder as an expression.
This patch amends that.

Author: djdv

src/make.bat

@@ -77,7 +77,7 @@ if not "x%GOROOT_BOOTSTRAP%"=="x" goto bootstrapset
 for /f "tokens=*" %%g in ('where go 2^>nul') do (
 	if "x%GOROOT_BOOTSTRAP%"=="x" (
 		for /f "tokens=*" %%i in ('%%g env GOROOT 2^>nul') do (
-			if /I not %%i==%GOROOT_TEMP% (
+			if /I not "%%i"=="%GOROOT_TEMP%" (
 				set GOROOT_BOOTSTRAP=%%i
 			)
 		)