Get sdktools and sdkhooks/dhooks to load on hl2sdk-mock (#1892)

* Build SDKTools for hl2sdk-mock

* Fix loading of extensions using advanced naming scheme for hl2sdk-mock

* Fix error on missing sv_visiblemaxplayers convar

* Build SDKHooks for hl2sdk-mock

* Fix x86_64 SourcePawn VM filename

* SDKHooks: Ignore missing IEntityListeners list in hl2sdk-mock

extensions/sdktools/AMBuilder

@@ -41,8 +41,6 @@ for sdk_name in SM.sdks:
   for cxx in builder.targets:
     if not cxx.target.arch in sdk.platformSpec[cxx.target.platform]:
       continue
-    if sdk_name == 'mock':
-      continue
 
     binary = SM.HL2ExtConfig(project, builder, cxx, 'sdktools.ext.' + sdk.ext, sdk)
     binary.compiler.cxxincludes += [