fix: SLIC3R_PCH=OFF now builds on Windows, allowing compiler caching (#15552)

scripts/test_build_win.ps1

@@ -92,6 +92,12 @@ New-Item -ItemType Directory -Force -Path $clangDir | Out-Null
 Copy-Item "$env:SystemRoot\System32\where.exe" (Join-Path $clangDir 'clang-cl.exe') -Force
 $clangOnPath = "$clangDir;$env:PATH"
 
+# A ccache that only has to exist. Nothing runs it; the script only locates it.
+$cacheDir = Join-Path $fixtures 'cache'
+New-Item -ItemType Directory -Force -Path $cacheDir | Out-Null
+Copy-Item "$env:SystemRoot\System32\where.exe" (Join-Path $cacheDir 'ccache.exe') -Force
+$ccacheOnPath = "$cacheDir;$env:PATH"
+
 # ProgramFiles(x86) is where the script looks for vswhere, so an empty one
 # stands in for a machine whose Visual Studio has no clang toolset.
 $noVs = Join-Path $fixtures 'no-vs'
@@ -121,7 +127,7 @@ $cases = @(
                     'Examples:', 'Environment:')  }
     @{ Name = 'the environment section shows what to set'; Args = @('--help'); DryRun = $false
        Contains = @('ORCA_DEPS_CMAKE_ARGS', 'ORCA_SLICER_CMAKE_ARGS', 'ORCA_UPDATER_SIG_KEY', 'NINJA_STATUS',
-                    'set ORCA_SLICER_CMAKE_ARGS=-DSLIC3R_PCH=OFF', '(PowerShell)', 'debugscript') }
+                    'set ORCA_SLICER_CMAKE_ARGS=-DSLIC3R_BUILD_SANDBOXES=ON', '(PowerShell)', 'debugscript') }
     @{ Name = 'section headers do not widen the flag column'; Args = @('--help'); DryRun = $false
        Match = @('^   -d, --deps  +Download') }
     # Windows Terminal opens at 120 columns and wraps at 120, so 119 is the
@@ -294,6 +300,14 @@ $cases = @(
        Contains = @('-DBUILD_TESTS=ON') }
     @{ Name = '-a enables ASAN for the slicer'; Args = @('-s', '-a')
        Contains = @('-DSLIC3R_ASAN=ON') }
+    @{ Name = '--no-pch turns the precompiled header off'; Args = @('-s', '--no-pch')
+       Contains = @('-DSLIC3R_PCH=OFF') }
+    @{ Name = '--no-pch says so in the banner'; Args = @('-s', '--no-pch')
+       Contains = @('Precompiled header: off') }
+    @{ Name = 'the precompiled header is on unless asked'; Args = @('-s')
+       NotContains = @('SLIC3R_PCH') }
+    @{ Name = '--no-pch works without a cache'; Args = @('-s', '--no-pch')
+       NotContains = @('COMPILER_LAUNCHER') }
     @{ Name = 'the slicer build runs gettext'; Args = @('-s')
        Contains = @('run_gettext.bat') }
     # tools\7z.exe needs a 7z.dll beside it, which the repo does not carry,
@@ -324,6 +338,42 @@ $cases = @(
     @{ Name = 'deps and slicer build in one invocation'; Args = @('-d', '-s', '-x', '-l')
        Contains = @('cmake -S deps', 'cmake -B "build-clang" ') }
 
+    'the compiler cache'
+    @{ Name = '--cache needs clang-cl and Ninja'; Args = @('-s', '--cache', 'ccache'); ExpectExit = 1
+       Contains = @('needs clang-cl and Ninja') }
+    # cl.exe is out of scope, since ccache refuses every compile under /Zi.
+    @{ Name = '--cache under Ninja still needs clang-cl'; Args = @('-s', '-x', '--cache', 'ccache'); ExpectExit = 1
+       Contains = @('needs clang-cl and Ninja') }
+    @{ Name = 'an unknown --cache value is rejected'; Args = @('-s', '-x', '--cache', 'nope'); ExpectExit = 1
+       Contains = @('Expected ccache, sccache or off') }
+    # A bare PATH, since the machine running the tests may have sccache installed.
+    @{ Name = 'a --cache tool that is not there is caught early'; Args = @('-s', '-l', '-x', '--cache', 'sccache'); ExpectExit = 1
+       Env = @{ PATH = 'C:\Windows\system32;C:\Windows' }
+       Contains = @('is not on PATH') }
+    @{ Name = '--cache takes any casing'; Args = @('-s', '-l', '-x', '--cache', 'CCACHE')
+       Env = @{ PATH = $ccacheOnPath }
+       Contains = @('ccache.exe') }
+    @{ Name = '--cache off asks for no launcher'; Args = @('-s', '-x', '--cache', 'off')
+       NotContains = @('COMPILER_LAUNCHER') }
+    @{ Name = 'no --cache asks for no launcher'; Args = @('-s', '-x')
+       NotContains = @('COMPILER_LAUNCHER') }
+    @{ Name = '--cache turns the precompiled header off'; Args = @('-s', '-l', '-x', '--cache', 'ccache')
+       Env = @{ PATH = $ccacheOnPath }
+       Contains = @('-DSLIC3R_PCH=OFF', 'COMPILER_LAUNCHER') }
+    # The resolved path, not the bare name, so PATH cannot change it later.
+    @{ Name = '--cache names the resolved path in the banner'; Args = @('-s', '-l', '-x', '--cache', 'ccache')
+       Env = @{ PATH = $ccacheOnPath }
+       Match = @('^Compiler cache: .*/ccache\.exe$') }
+    @{ Name = '--cache reaches the dependency configure too'; Args = @('-d', '-l', '-x', '--cache', 'ccache')
+       Env = @{ PATH = $ccacheOnPath }
+       Contains = @('-DCMAKE_C_COMPILER_LAUNCHER=') }
+    # Nothing records a launcher without a configure, so the tool is not needed.
+    # Reaching the cmake check on a bare PATH is what proves it was skipped.
+    @{ Name = '--no-configure asks for no cache tool'; Args = @('-s', '-l', '-x', '--no-configure', '--cache', 'ccache'); ExpectExit = 1
+       Env = @{ PATH = 'C:\Windows\system32;C:\Windows' }
+       Contains = @('CMake was not found')
+       NotContains = @('is not on PATH') }
+
     'the developer loop'
     @{ Name = '--slicer-target builds one target'; Args = @('-s', '--slicer-target', 'libslic3r')
        Contains = @('--config Release --target libslic3r') }