.build/build.ps1: return to working dir even after an error

When testing the script locally in PowerShell console, I noticed that if
one of the commands fails and causes the termination of the script, the
last command `Pop-Location` is not executed and thus the working
directory in the PowerShell console remains `$repoRoot\build`. From the
user's point of view, this means that the script changed their working
directory, which is annoying.

For example, here is how the old version of the script behaves in a
PowerShell session if the `build/` folder is not writable:

```
PS C:\temp\kaitai_struct\runtime\cpp_stl> .\.build\build.ps1 -GTestPath C:\temp\vcpkg\installed\x64-windows
Re-run cmake no build system arguments
CMake Error: Unable to (re)create the private pkgRedirects directory:
C:/temp/kaitai_struct/runtime/cpp_stl/build/CMakeFiles/pkgRedirects
Exception: C:\temp\kaitai_struct\runtime\cpp_stl\.build\build.ps1:35
Line |
  35 |      throw "'cmake' exited with code $LastExitCode"
     |      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | 'cmake' exited with code 1
PS C:\temp\kaitai_struct\runtime\cpp_stl\build>
```

Notice that the original prompt was
`PS C:\temp\kaitai_struct\runtime\cpp_stl>`, but the new prompt is
`PS C:\temp\kaitai_struct\runtime\cpp_stl\build>`.

This commit fixes this issue by ensuring that `Pop-Location` runs
regardless of whether any previous command failed.

.build/build.ps1

@@ -25,22 +25,24 @@ $PSDefaultParameterValues['*:ErrorAction'] = 'Stop'
 $repoRoot = (Resolve-Path "$PSScriptRoot\..").Path
 Push-Location $repoRoot
 
-$null = New-Item -Path build -ItemType Directory -Force
-cd build
-
-$env:VERBOSE = '1'
-
-cmake -DCMAKE_PREFIX_PATH="$GTestPath" -DSTRING_ENCODING_TYPE="$EncodingType" ..
-if ($LastExitCode -ne 0) {
-    throw "'cmake' exited with code $LastExitCode"
-}
-
-cmake --build . --config Debug
-if ($LastExitCode -ne 0) {
-    throw "'cmake --build' exited with code $LastExitCode"
+try {
+    $null = New-Item -Path build -ItemType Directory -Force
+    cd build
+
+    $env:VERBOSE = '1'
+
+    cmake -DCMAKE_PREFIX_PATH="$GTestPath" -DSTRING_ENCODING_TYPE="$EncodingType" ..
+    if ($LastExitCode -ne 0) {
+        throw "'cmake' exited with code $LastExitCode"
+    }
+
+    cmake --build . --config Debug
+    if ($LastExitCode -ne 0) {
+        throw "'cmake --build' exited with code $LastExitCode"
+    }
+
+    cp $GTestPath\debug\bin\*.dll tests\Debug
+    cp Debug\kaitai_struct_cpp_stl_runtime.dll tests\Debug
+} finally {
+    Pop-Location
 }
-
-cp $GTestPath\debug\bin\*.dll tests\Debug
-cp Debug\kaitai_struct_cpp_stl_runtime.dll tests\Debug
-
-Pop-Location