[CI] Use proper POWERSHELL variable casing

The POWERSHELL cmake variable was sometimes used lowercase.

CMakeLists.txt

@@ -58,7 +58,7 @@ if(WIN32)
         HINTS "/Windows/System32/WindowsPowerShell/v1.0"
         REQUIRED)
 else()
-    find_program(powershell pwsh REQUIRED)
+    find_program(POWERSHELL pwsh REQUIRED)
 endif()
 
 include(Set-Toolchain-vcpkg)

cmake/MakeReleaseCommitAndTag.cmake

@@ -189,7 +189,7 @@ Ignore the following cmake error.
 
     if(CMAKE_HOST_SYSTEM MATCHES Windows OR ((NOT DEFINED CMAKE_HOST_SYSTEM) AND WIN32))
         execute_process(
-            COMMAND powershell -NoLogo -NoProfile -ExecutionPolicy Bypass -Command [=[
+            COMMAND ${POWERSHELL} -NoLogo -NoProfile -ExecutionPolicy Bypass -Command [=[
                 $text = [IO.File]::ReadAllText("CHANGELOG.md.work") -replace "`r`n", "`n"
                 [IO.File]::WriteAllText("CHANGELOG.md", $text)
             ]=]

cmake/Set-Toolchain-vcpkg.cmake

@@ -319,7 +319,7 @@ function(get_binary_packages vcpkg_exe)
 
 #                -command "import-module ($env:USERPROFILE + '/source/repos/vcpkg-binpkg-prototype/vcpkg-binpkg.psm1'); vcpkg-instpkg ."
         execute_process(
-            COMMAND ${powershell}
+            COMMAND ${POWERSHELL}
                 -executionpolicy bypass -noprofile
                 -command "import-module '${CMAKE_BINARY_DIR}/vcpkg-binpkg/vcpkg-binpkg.psm1'; vcpkg-instpkg ."
             WORKING_DIRECTORY ${bin_pkgs_dir}

cmake/UpdateAppcast.cmake

@@ -84,7 +84,7 @@ Ignore the following cmake error.
 
     if(CMAKE_HOST_SYSTEM MATCHES Windows OR ((NOT DEFINED CMAKE_HOST_SYSTEM) AND WIN32))
         execute_process(
-            COMMAND powershell -NoLogo -NoProfile -ExecutionPolicy Bypass -Command [=[
+            COMMAND ${POWERSHELL} -NoLogo -NoProfile -ExecutionPolicy Bypass -Command [=[
                 $text = [IO.File]::ReadAllText("appcast.xml.work") -replace "`r`n", "`n"
                 [IO.File]::WriteAllText("appcast.xml", $text)
             ]=]