[HCT] Build DXC with VS 2026 by default (#8187)

Visual Studio 2026 recently released. The hct utilities build DXC with
the 2022 release by default.
This PR updates the hctbuild batch script so that the 2026 visual studio
solution generator is used instead by default.
A new option was added to specify the 2022 release if desired.
The build pipelines remain building with 2022 until the vm image that
targets 2026 is released.

Author: bob80905

azure-pipelines.yml

@@ -36,7 +36,7 @@ stages:
       submodules: true
     - script: |
         call utils\hct\hctstart.cmd %HLSL_SRC_DIR% %HLSL_BLD_DIR%
-        call utils\hct\hctbuild.cmd -$(platform) -$(configuration) -show-cmake-log -spirvtest -warp-nuget-version 1.0.16.1
+        call utils\hct\hctbuild.cmd -vs2022 -$(platform) -$(configuration) -show-cmake-log -spirvtest -warp-nuget-version 1.0.16.1
       displayName: 'Building'
     - script: |
         call utils\hct\hctstart.cmd %HLSL_SRC_DIR% %HLSL_BLD_DIR%

utils/hct/hctbuild.cmd

@@ -22,7 +22,7 @@ if "%BUILD_ARCH%"=="" (
   set BUILD_ARCH=Win32
 )
 
-set BUILD_GENERATOR=Visual Studio 17 2022
+set BUILD_GENERATOR=Visual Studio 18 2026
 set BUILD_VS_VER=2022
 set BUILD_CONFIG=Debug
 set DO_SETUP=1
@@ -136,6 +136,11 @@ if "%1"=="-vs2019" (
   shift /1 & goto :parse_args
 )
 if "%1"=="-vs2022" (
+  set BUILD_GENERATOR=Visual Studio 17 2022
+  set BUILD_VS_VER=2022
+  shift /1 & goto :parse_args
+)
+if "%1"=="-vs2026" (
   shift /1 & goto :parse_args
 )
 if "%1"=="-tblgen" (
@@ -442,6 +447,7 @@ echo   -no-parallel   disables parallel build
 echo   -no-dxilconv   disables build of DXBC to DXIL converter and tools
 echo   -vs2019        uses Visual Studio 2019 to build
 echo   -vs2022        uses Visual Studio 2022 to build
+echo   -vs2026        uses Visual Studio 2026 to build
 echo.
 echo   -update-generated-sources   Updates generated sources in the source tree
 echo.