[installers] Share installer payload generation logic

[pjcollins]

Introduces a new create-pkg project next to create-vsix to be used
in a similar way to create a macOS installer for xamarin-android. The
build-tools/installers/create-installers.targets file has also been
added to keep track of all of the content we require in both our macOS
and Windows installers. These shared items, properties, and targets are
used by both installer projects to ensure uniformity between the two
installers we produce.

The ConstructInstallerItems target determines the majority of the files
which should end up in the installer. Behavior will vary depending on the
existance of certain files or the values of certain msbuild properties.
This was done intentionally to be able to support creating installers for
PR builds, open source packages, and commercial packages.

The AndroidFirstFrameworkVersion, AndroidLatestStableFrameworkVersion,
and AndroidLatestFrameworkVersion MSBuild properties (along with some
hardcoded values) are used to determine which API levels the installer
will support.

The AndroidSupportedTargetJitAbi MSBuild property is used to determine
which Android ABIs the installer will support.

The IncludeMonoBundleComponents MSBuild property is used to determine
whether or not the components which come from a full mono integration
build should be included in the installers.

The new create-installers make target will attempt to package all of
the relevant files for every ABI specified in the ALL_JIT_ABIS variable
in build-tools/scripts/BuildEverything.mk. This behavior can be
overridden by specifying an empty value for _MSBUILD_ARGS when calling
the create-installers make rule (as build.groovy does), or by providing
an alternate value for /p:AndroidSupportedTargetJitAbis when building
either installer directly from MSBuild.

The build.groovy script has been updated to handle creating different
installer types for PR builds and full builds. Our macOS PR builds will
now build a mxe-win flavored version of libmono-android, so that it can
be included in a vsix installer and used to extend test coverage for our
PR builds in the future. PR builds will also package a limited set of
Android ABI support as briefly mentioned above.

A new pkg preinstall script has also been added to fix an issue that
would result in old installations being left on disk. Now, the macOS
installer will attempt to remove the version currently symlinked to
/Library/Frameworks/Xamarin.Android.framework/Versions/Current
before running.

Fixes #2686.

[pjcollins]

Initial testing of a .pkg produced by this new create-pkg project has produced positive results with a couple of XA projects (build/package/deploy) from both command line msbuild and VS Mac.

[jonpryor]

It occurs to me that build-tools/scripts has become a bit of a mish-mash of...things...and that it would be better if we had more semantically meaningful names and descriptions.

As such, instead of build-tools/scripts/installers/create-installers.targets, could we "flatten" that into build-tools/installers/create-installers.targets (removing the scripts portion entirely).

[jonpryor]

This should also update build-tools/automation/build.groovy so that the .pkg is created and uploaded, e.g. (untested)

diff --git a/build-tools/automation/build.groovy b/build-tools/automation/build.groovy
index dd58d6cc..fe57e8ab 100644
--- a/build-tools/automation/build.groovy
+++ b/build-tools/automation/build.groovy
@@ -97,6 +97,10 @@ timestamps {
             sh "make create-vsix CONFIGURATION=${env.BuildFlavor}"
         }
 
+        stageWithTimeout('create pkg', 30, 'MINUTES', XADir, true) {    // Typically takes less than 5 minutes
+            sh "msbuild /p:Configuration=${env.BuildFlavor} /t:CreatePkg build-tools/create-pkg/create-pkg.csproj"
+        }
+
         stageWithTimeout('build tests', 30, 'MINUTES', XADir, true) {    // Typically takes less than 10 minutes
             sh "make all-tests CONFIGURATION=${env.BuildFlavor}"
         }
@@ -111,7 +115,7 @@ timestamps {
         }
 
         stageWithTimeout('publish packages to Azure', 10, 'MINUTES', XADir, true) {    // Typically takes less than a minute
-            def publishBuildFilePaths = "xamarin.android-oss*.zip,bin/${env.BuildFlavor}/bundle-*.zip,bin/Build*/Xamarin.Android.Sdk*.vsix,prepare-image-dependencies.sh,build-status*,xa-build-status*";
+            def publishBuildFilePaths = "xamarin.android-oss*.zip,bin/${env.BuildFlavor}/bundle-*.zip,bin/Build*/Xamarin.Android.Sdk*.vsix,bin/Build*/*.pkg,prepare-image-dependencies.sh,build-status*,xa-build-status*";
             echo "publishBuildFilePaths: ${publishBuildFilePaths}"
             def stageStatus = publishPackages(publishBuildFilePaths)
             if (stageStatus != 0) {

[jonpryor]

There are merge conflicts. :-(

Additionally, commit f74cd44 added some additional files which should be installed:

• xbuild\Xamarin\Android\jit-times.exe
• xbuild\Xamarin\Android\$(HostOS)\jit-times

[pjcollins]

@jonpryor I'm also working on another required make change, we'll need to override AndroidSupportedTargetJitAbis when creating installers for a non PR build.

[jonpryor]

Why is this overriding _MSBUILD_ARGS and not MSBUILD_ARGS?