Clear Cmake defines on reuse of hctbuild (#2659)

After initial generation, subsequent invocations of cmake will
only alter the defines that are specified by that command. Any
defines that were set previously retain their earlier settings
by being stored in the CMakeCache.txt in the build directory.

hctbuild.cmd allows specifying certain defines when arguments are
passed to it, but many of these do not allow resetting the defines
they set. So if you define an official versioned build, every
subsequent build with use the official version unless the cmake
cache is edited or the whole build directory is wiped clean. This
is true of several other settings.

This change sets the defines hctbuild cares about every time it is
invoked regardless of arguments. If the official build is specified
the official define is set to ON. If it isn't, it is set to OFF.
This way these flags can easily be switched on the same build dir.

utils/hct/hctbuild.cmd

@@ -48,6 +48,14 @@ set DO_BUILD=1
 set CMAKE_OPTS=
 set SPEAK=1
 set PARALLEL_OPT=
+set ALL_DEFS=OFF
+set ANALYZE=OFF
+set OFFICIAL=OFF
+set FIXED_VER=OFF
+set FIXED_LOC=
+set VENDOR=
+set SPIRV=OFF
+set SPV_TEST=OFF
 
 if "%1"=="-s" (
   set DO_BUILD=0
@@ -57,33 +65,35 @@ if "%1"=="-b" (
   set DO_SETUP=0
   shift /1
 )
+
 if "%1"=="-alldef" (
-  set CMAKE_OPTS=-DHLSL_OPTIONAL_PROJS_IN_DEFAULT:BOOL=ON
+  set ALL_DEFS=ON
   shift /1
 )
 if "%1"=="-analyze" (
-  set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_ANALYZE:BOOL=ON
+  set ANALYZE=ON
   shift /1
 )
 if "%1"=="-official" (
   echo Will generate official version for build
-  set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_OFFICIAL_BUILD:BOOL=ON
+  set OFFICIAL=ON
   shift /1
 )
 if "%1"=="-fv" (
   echo Fixed version flag set for build.
-  set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_FIXED_VER:BOOL=ON
+  set FIXED_VER=ON
   shift /1
 )
 if "%1"=="-fvloc" (
   echo Fixed version flag set for build, version file location: %2
-  set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_FIXED_VER:BOOL=ON -DHLSL_FIXED_VERSION_LOCATION:STRING=%2
+  set FIXED_VER=ON
+  set FIXED_LOC=%2
   shift /1
   shift /1
 )
 if "%1"=="-cv" (
   echo Set the CLANG_VENDOR value.
-  set CMAKE_OPTS=%CMAKE_OPTS% -DCLANG_VENDOR:STRING=%2
+  set VENDOR=%2
   shift /1
   shift /1
 )
@@ -162,12 +172,12 @@ if "%BUILD_VS_VER%"=="2015" (
 rem Begin SPIRV change
 if "%1"=="-spirv" (
   echo SPIR-V codegen is enabled.
-  set CMAKE_OPTS=%CMAKE_OPTS% -DENABLE_SPIRV_CODEGEN:BOOL=ON
+  set SPIRV=ON
   shift /1
 )
 if "%1"=="-spirvtest" (
   echo Building SPIR-V tests is enabled.
-  set CMAKE_OPTS=%CMAKE_OPTS% -DSPIRV_BUILD_TESTS:BOOL=ON
+  set SPV_TEST=ON
   shift /1
 )
 rem End SPIRV change
@@ -197,6 +207,14 @@ if "%1"=="-ninja" (
   shift /1
 )
 
+set CMAKE_OPTS=-DHLSL_OPTIONAL_PROJS_IN_DEFAULT:BOOL=%ALL_DEFS%
+set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_ANALYZE:BOOL=%ANALYZE%
+set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_OFFICIAL_BUILD:BOOL=%OFFICIAL%
+set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_FIXED_VER:BOOL=%FIXED_VER%
+set CMAKE_OPTS=%CMAKE_OPTS% -DHLSL_ENABLE_FIXED_VER:BOOL=%FIXED_VER% -DHLSL_FIXED_VERSION_LOCATION:STRING=%FIXED_LOC%
+set CMAKE_OPTS=%CMAKE_OPTS% -DCLANG_VENDOR:STRING=%VENDOR%
+set CMAKE_OPTS=%CMAKE_OPTS% -DENABLE_SPIRV_CODEGEN:BOOL=%SPIRV%
+set CMAKE_OPTS=%CMAKE_OPTS% -DSPIRV_BUILD_TESTS:BOOL=%SPV_TEST%
 set CMAKE_OPTS=%CMAKE_OPTS% -DCLANG_ENABLE_ARCMT:BOOL=OFF
 set CMAKE_OPTS=%CMAKE_OPTS% -DCLANG_ENABLE_STATIC_ANALYZER:BOOL=OFF
 set CMAKE_OPTS=%CMAKE_OPTS% -DCLANG_INCLUDE_TESTS:BOOL=OFF -DLLVM_INCLUDE_TESTS:BOOL=OFF