build: add DocC to the default built

DocC is not yet part of the distribution on Windows as we are
progressing towards passing the test suite.  However, other products
were released before the test suites were completely passing and that
would remain an option here.  Begin building this tool as part of the
build as it is meant to be part of the distribution.

Author: compnerd

build.ps1

@@ -1341,6 +1341,16 @@ function Build-Format() {
     -Arch $HostArch
 }
 
+function Build-DocC() {
+  $OutDir = Join-Path -Path $HostArch.BinaryRoot -ChildPath swift-docc
+
+  Build-SPMProject `
+    -Src $SourceCache\swift-docc `
+    -Bin $OutDir `
+    -Arch $HostArch `
+    --product docc
+}
+
 function Build-Installer() {
   Build-WiXProject bld.wixproj -Arch $HostArch -Properties @{
     DEVTOOLS_ROOT = "$($HostArch.ToolchainInstallRoot)\";
@@ -1446,6 +1456,7 @@ Install-HostToolchain
 if (-not $SkipBuild) {
   Build-Inspect $HostArch
   Build-Format $HostArch
+  Build-DocC $HostArch
 }
 
 if (-not $SkipPackaging) {