Adapt appveyor.yml for the new unified build

Reviewed-by: Rich Salz <rsalz@openssl.org>

appveyor.yml

@@ -15,28 +15,19 @@ before_build:
         If ($env:Platform -Match "x86") {
             $env:VCVARS_PLATFORM="x86"
             $env:TARGET="VC-WIN32"
-            $env:DO="do_ms"
         } Else {
             $env:VCVARS_PLATFORM="amd64"
             $env:TARGET="VC-WIN64A"
-            $env:DO="do_win64a"
-        }
-    - ps: >-
-        If ($env:Configuration -Like "*shared*") {
-            $env:MAK="ntdll.mak"
-        } Else {
-            $env:MAK="nt.mak"
         }
     - ps: $env:VSCOMNTOOLS=(Get-Content ("env:VS" + "$env:VSVER" + "0COMNTOOLS"))
     - call "%VSCOMNTOOLS%\..\..\VC\vcvarsall.bat" %VCVARS_PLATFORM%
     - perl Configure %TARGET% no-asm
-    - call ms\%DO%
 
 build_script:
-    - nmake /f ms\%MAK%
+    - nmake
 
 test_script:
-    - nmake /f ms\%MAK% test
+    - nmake test
 
 notifications:
     - provider: Email