Call MSBuild in x86 build with Win32 platform.

build/scripts/Build.lua

@@ -13,7 +13,7 @@ function get_msbuild_path()
 	error("MSBuild path could not be found in Windows registry.")
 end
 
-function msbuild(sln, conf)
+function msbuild(sln, conf, platform)
 	local msbuild_path = "msbuild.exe"
 	local sln = path.normalize(sln)
 
@@ -22,6 +22,10 @@ function msbuild(sln, conf)
 		cmd = cmd .. " /p:Configuration=" .. conf
 	end
 
+	if platform ~= nil then
+		cmd = cmd .. " /p:Platform=" .. platform
+	end
+
 	execute_or_die(cmd)
 end
 

build/scripts/LLVM.lua

@@ -383,7 +383,11 @@ function build_llvm(llvm_build)
 		local cmake_generator, options = get_cmake_generator()
 		cmake(cmake_generator, conf, llvm_build, options)
 		local llvm_sln = path.join(llvm_build, "LLVM.sln")
-		msbuild('"' .. llvm_sln .. '"', conf)
+		platform = nil
+		if target_architecture() == "x86" then
+			platform = "Win32"
+		end
+		msbuild('"' .. llvm_sln .. '"', conf, platform)
 	else
 		local options = os.ishost("macosx") and
 			"-DLLVM_ENABLE_LIBCXX=true" or ""