build: put the toolchain extraction logs into the build tree

Use an absolute path to ensure that we do not place the logs in the
current directory.

Author: compnerd

utils/build.ps1

@@ -447,7 +447,7 @@ function Fetch-Dependencies {
   Get-ChildItem "$BinaryCache\toolchains\WixAttachedContainer" -Filter "*.msi" | % {
     $LogFile = [System.IO.Path]::ChangeExtension($_.Name, "log")
     $TARGETDIR = if ($_.Name -eq "rtl.msi") { "$BinaryCache\toolchains\$PinnedToolchain\LocalApp\Programs\Swift\Runtimes\0.0.0\usr\bin" } else { "$BinaryCache\toolchains\$PinnedToolchain" }
-    Invoke-Program -OutNull msiexec.exe /lvx! $LogFile /qn /a $BinaryCache\toolchains\WixAttachedContainer\$_ ALLUSERS=0 TARGETDIR=$TARGETDIR
+    Invoke-Program -OutNull msiexec.exe /lvx! $BinaryCache\toolchains\$LogFile /qn /a $BinaryCache\toolchains\WixAttachedContainer\$_ ALLUSERS=0 TARGETDIR=$TARGETDIR
   }
 
   if ($WinSDKVersion) {