utils: tweak cmark wiring

Use the installed image rather than the build tree for wiring up CMark.
This may be used across phases of the build, so it is better to use the
staged image.

Author: compnerd

utils/build.ps1

@@ -902,7 +902,7 @@ function Build-BuildTools($Arch) {
       SWIFT_INCLUDE_APINOTES = "NO";
       SWIFT_INCLUDE_DOCS = "NO";
       SWIFT_INCLUDE_TESTS = "NO";
-      "cmark-gfm_DIR" = "$($HostArch.BinaryCache)\cmark-gfm-0.29.0.gfm.13";
+      "cmark-gfm_DIR" = "$($Arch.ToolchainInstallRoot)\usr\lib\cmake";
     }
 }
 
@@ -1621,7 +1621,7 @@ function Build-Markdown($Arch) {
     -Defines @{
       BUILD_SHARED_LIBS = "NO";
       ArgumentParser_DIR = "$BinaryCache\6\cmake\modules";
-      "cmark-gfm_DIR" = "$($Arch.BinaryCache)\cmark-gfm-0.29.0.gfm.13";
+      "cmark-gfm_DIR" = "$($Arch.ToolchainInstallRoot)\usr\lib\cmake";
     }
 }
 
@@ -1639,7 +1639,7 @@ function Build-Format($Arch) {
       BUILD_SHARED_LIBS = "YES";
       ArgumentParser_DIR = "$BinaryCache\6\cmake\modules";
       SwiftSyntax_DIR = "$BinaryCache\1\cmake\modules";
-      "cmark-gfm_DIR" = "$($Arch.BinaryCache)\cmark-gfm-0.29.0.gfm.13";
+      "cmark-gfm_DIR" = "$($Arch.ToolchainInstallRoot)\usr\lib\cmake";
       SwiftMarkdown_DIR = "$BinaryCache\13\cmake\modules";
     }
 }