Xamarin.Android build preparation utility

Testing:

 * Default mode: run `make bootstrap`
 * Verbose debug: run `make V=1 bootstrap`
 * CI mode: run `make BOOTSTRAP_CI=1 bootstrap`
 * Help: run `make bootstrap-help`
 * Logs: `bin/BuildDebug/logs/`

Supported operating systems:

 * macOS
 * Linux

Windows support is planned, present but not fully implemented or tested.

This commit implements a `make prepare` replacement that does not rely on shell
scripts or MSBuild. The idea is that a standalone C# program can perform all the
steps in a more streamlined, more clear way than the current solution. One of
the main goals is to make the process more approachable by external
contributors, but also by the core developers who may want to change some
aspects of XA build preparation (e.g. Android platforms, Mono version etc) but
are not familiar with the build system. Towards that goal, the codebase is
designed so that the minimum amount of searching around it is necessary to
figure out where to make the desired change. Main location serving this purpose
is the `build-tools/xabootstrap/xabootstrap/ConfigAndData` directory. It should
be the *only* location where one needs to look in order to change all and any
aspects of XA preparation.

[TBC]

Author: grendello

CODEOWNERS

@@ -20,6 +20,7 @@
 /build-tools/manifest-attribute-codegen @jonpryor
 /build-tools/scripts/PrepareWindows.targets @jonathanpeppers
 /build-tools/timing @jonathanpeppers @radekdoulik
+/build-tools/xabootstrap @grendello
 
 /src/OpenTK-1.0 @radekdoulik @jonpryor
 /src/Mono.Android.Export @jonpryor

Configuration.props

@@ -38,12 +38,16 @@
     <AndroidUseLatestPlatformSdk Condition=" '$(AndroidFrameworkVersion)' == '' And '$(_IsRunningNuGetRestore)' == 'True' ">True</AndroidUseLatestPlatformSdk>
     <DebugType Condition=" '$(DebugType)' == '' ">portable</DebugType>
   </PropertyGroup>
+  <PropertyGroup Condition=" '$(HostOS)' == '' ">
+    <HostOS Condition="$([MSBuild]::IsOSPlatform('windows'))">Windows</HostOS>
+    <HostOS Condition="$([MSBuild]::IsOSPlatform('linux'))">Linux</HostOS>
+    <HostOS Condition="$([MSBuild]::IsOSPlatform('osx'))">Darwin</HostOS>
+  </PropertyGroup>
   <PropertyGroup>
     <AutoProvision Condition=" '$(AutoProvision)' == '' ">False</AutoProvision>
     <AutoProvisionUsesSudo Condition=" '$(AutoProvisionUsesSudo)' == '' ">False</AutoProvisionUsesSudo>
     <XAInstallPrefix Condition=" '$(XAInstallPrefix)' == '' ">$(MSBuildThisFileDirectory)bin\$(Configuration)\lib\xamarin.android\</XAInstallPrefix>
     <MingwDependenciesRootDirectory Condition=" '$(MingwDependenciesRootDirectory)' == '' ">$(MSBuildThisFileDirectory)\bin\Build$(Configuration)\mingw-deps</MingwDependenciesRootDirectory>
-    <HostOS Condition=" '$(HostOS)' == '' And '$(OS)' == 'Windows_NT' ">Windows</HostOS>
     <HostCc Condition=" '$(HostCc)' == '' ">$(HostCc64)</HostCc>
     <HostCxx Condition=" '$(HostCxx)' == '' ">$(HostCxx64)</HostCxx>
     <HostCc Condition=" '$(HostCc)' == '' ">$(HostCc32)</HostCc>
@@ -171,7 +175,8 @@
     <AndroidSupportedTargetAotAbisSplit>$(AndroidSupportedTargetAotAbis.Split(':'))</AndroidSupportedTargetAotAbisSplit>
   </PropertyGroup>
   <PropertyGroup>
-    <RemapAssemblyRefTool>$(ManagedRuntime) $(ManagedRuntimeArgs) &quot;$(MSBuildThisFileDirectory)bin\Build$(Configuration)\remap-assembly-ref.exe&quot;</RemapAssemblyRefTool>
+    <RemapAssemblyRefToolExecutable>$(MSBuildThisFileDirectory)bin\Build$(Configuration)\remap-assembly-ref.exe</RemapAssemblyRefToolExecutable>
+    <RemapAssemblyRefTool>$(ManagedRuntime) $(ManagedRuntimeArgs) &quot;$(RemapAssemblyRefToolExecutable)&quot;</RemapAssemblyRefTool>
   </PropertyGroup>
 
   <!-- Unit Test Properties -->

Makefile

@@ -1,28 +1,59 @@
-export OS_NAME       := $(shell uname)
-export OS_ARCH       := $(shell uname -m)
-export NO_SUDO       ?= false
 V             ?= 0
 prefix         = /usr/local
 CONFIGURATION  = Debug
 RUNTIME       := $(shell which mono64 2> /dev/null && echo mono64 || echo mono) --debug=casts
 SOLUTION       = Xamarin.Android.sln
 TEST_TARGETS   = build-tools/scripts/RunTests.targets
 API_LEVEL     ?=
+BOOTSTRAP_ARGS =
+BOOTSTRAP_BUILD_LOG = bin/Build$(CONFIGURATION)/logs/bootstrap-build.binlog
+BOOTSTRAP_SOURCE_DIR = build-tools/xabootstrap
+BOOTSTRAP_SOLUTION = $(BOOTSTRAP_SOURCE_DIR)/xabootstrap.sln
+BOOTSTRAP_EXE = $(BOOTSTRAP_SOURCE_DIR)/xabootstrap/bin/$(CONFIGURATION)/xabootstrap.exe
+BOOTSTRAP_MSBUILD_ARGS = /p:Configuration=$(CONFIGURATION) /binaryLogger:"$(BOOTSTRAP_BUILD_LOG)"
+BOOTSTRAP_CI ?= 0
 
-ifeq ($(OS_NAME),Darwin)
-export MACOSX_DEPLOYMENT_TARGET := 10.11
-HOMEBREW_PREFIX ?= $(shell brew --prefix)
-else
-HOMEBREW_PREFIX := $prefix
+-include bin/Build$(CONFIGURATION)/rules.mk
+
+ifeq ($(OS_NAME),)
+export OS_NAME       := $(shell uname)
+endif
+
+ifeq ($(OS_ARCH),)
+export OS_ARCH       := $(shell uname -m)
+endif
+
+export NO_SUDO       ?= false
+
+ifneq ($(NO_SUDO),false)
+BOOTSTRAP_ARGS += --no-sudo
 endif
 
 ifneq ($(V),0)
 MONO_OPTIONS   += --debug
 NUGET_VERBOSITY = -Verbosity Detailed
+BOOTSTRAP_ARGS += -v:d
 endif
 
-ifneq ($(MONO_OPTIONS),)
-export MONO_OPTIONS
+ifneq($(BOOTSTRAP_CI),0)
+BOOTSTRAP_ARGS += --no-sudo --no-emoji --run-mode=CI
+endif
+
+ifeq ($(OS_NAME),Darwin)
+
+ifeq ($(MACOSX_DEPLOYMENT_TARGET),)
+export MACOSX_DEPLOYMENT_TARGET := 10.11
+endif
+
+ifeq ($(HOMEBREW_PREFIX),)
+HOMEBREW_PREFIX ?= $(shell brew --prefix)
+endif
+else
+HOMEBREW_PREFIX := $prefix
+endif
+
+ifeq ($(wildcard Configuration.OperatingSystem.props),)
+BOOTSTRAP_MSBUILD_ARGS += "/p:HostHomebrewPrefix=$(HOMEBREW_PREFIX)"
 endif
 
 include build-tools/scripts/msbuild.mk
@@ -257,3 +288,16 @@ list-nunit-tests:
 	$(MSBUILD) $(MSBUILD_FLAGS) $(TEST_TARGETS) /t:ListNUnitTests
 
 include build-tools/scripts/runtime-helpers.mk
+
+.PHONY: bootstrap-build
+bootstrap-build:
+	mkdir -p $(dir $(BOOTSTRAP_BUILD_LOG))
+	msbuild $(BOOTSTRAP_MSBUILD_ARGS) $(BOOTSTRAP_SOLUTION)
+
+bootstrap:
+	$(MAKE) bootstrap-build
+	mono --debug $(BOOTSTRAP_EXE) $(BOOTSTRAP_ARGS)
+
+bootstrap-help:
+	$(MAKE) bootstrap-build
+	mono --debug $(BOOTSTRAP_EXE) -h