Enable building on arm64 machines

With this commit, I can build core-sdk on RHEL 8 on arm64 directly,
without cross compilation.

Bump the sourcelink version to pick up the ability to parse git info
without depending on libgit2sharp. This allows sourcelink to work on
arm64. The version is the same as the one recently added to core-setup:
dotnet/core-setup#7696

Introduce a new 'BuildArchitecture' msbuild property that contains the host
architecture (arm64, x64, etc). This is the architecture of the
currently running machine, and may be different from the architecture we
are targetting in the case of cross compilation.

There's a gotcha with BuildArchitecture: under Visual Studio (an x86) process,
we generally want a x64 architecture. So try and restrict it to arm64 only.

Use BuildArchitecture to determine whether _crossDir and LibCLRJitRid need to
be special-cased for arm64 or or not.

Directory.Build.props

@@ -7,6 +7,12 @@
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
   </PropertyGroup>
 
+  <PropertyGroup>
+    <BuildArchitecture>$([System.Runtime.InteropServices.RuntimeInformation]::ProcessArchitecture.ToString().ToLowerInvariant())</BuildArchitecture>
+    <Architecture Condition="'$(BuildArchitecture)' == 'arm64'">$(BuildArchitecture)</Architecture>
+    <Architecture Condition="'$(Architecture)' == ''">x64</Architecture>
+  </PropertyGroup>
+
   <PropertyGroup>
     <TreatWarningsAsErrors>True</TreatWarningsAsErrors>
     <DebugType>embedded</DebugType>

src/redist/targets/Crossgen.targets

@@ -5,14 +5,14 @@
 
     <PropertyGroup>
       <RuntimeNETCoreAppPackageName>microsoft.netcore.app.runtime.$(SharedFrameworkRid)</RuntimeNETCoreAppPackageName>
-      <_crossDir Condition="'$(Architecture)' == 'arm64'">/x64_arm64</_crossDir>
+      <_crossDir Condition="'$(Architecture)' == 'arm64' and '$(BuildArchitecture)' != 'arm64'">/x64_arm64</_crossDir>
       <_crossDir Condition="'$(Architecture)' == 'arm' And '$(OSName)' == 'win'">/x86_arm</_crossDir>
       <_crossDir Condition="'$(Architecture)' == 'arm' And '$(OSName)' == 'linux'">/x64_arm</_crossDir>
       <CrossgenPath>$(NuGetPackageRoot)/$(RuntimeNETCoreAppPackageName)/$(MicrosoftNETCoreAppRuntimePackageVersion)/tools$(_crossDir)/crossgen$(ExeExtension)</CrossgenPath>
-      <LibCLRJitRid Condition="!$(Architecture.StartsWith('arm'))">$(SharedFrameworkRid)</LibCLRJitRid>
-      <LibCLRJitRid Condition="'$(Architecture)' == 'arm64'">x64_arm64</LibCLRJitRid>
+      <LibCLRJitRid Condition="'$(Architecture)' == 'arm64' and '$(BuildArchitecture)' == 'x64'">x64_arm64</LibCLRJitRid>
       <LibCLRJitRid Condition="'$(Architecture)' == 'arm' And '$(OSName)' == 'win'">x86_arm</LibCLRJitRid>
       <LibCLRJitRid Condition="'$(Architecture)' == 'arm' And '$(OSName)' == 'linux'">x64_arm</LibCLRJitRid>
+      <LibCLRJitRid Condition="'$(LibCLRJitRid)' == ''">$(SharedFrameworkRid)</LibCLRJitRid>
       <LibCLRJitPath>$(NuGetPackageRoot)/$(RuntimeNETCoreAppPackageName)/$(MicrosoftNETCoreAppRuntimePackageVersion)/runtimes/$(LibCLRJitRid)/native/$(DynamicLibPrefix)clrjit$(DynamicLibExtension)</LibCLRJitPath>
       <SharedFrameworkNameVersionPath>$(RedistLayoutPath)shared/$(SharedFrameworkName)/$(MicrosoftNETCoreAppRuntimePackageVersion)</SharedFrameworkNameVersionPath>
       <DIASymReaderCrossgenFilter>*</DIASymReaderCrossgenFilter>

src/redist/targets/GenerateLayout.targets

@@ -42,11 +42,11 @@
 
       <!-- Use the "x64" Rid when downloading Linux shared framework 'DEB' installer files. -->
       <SharedFrameworkInstallerFileRid>$(CoreSetupRid)</SharedFrameworkInstallerFileRid>
-      <SharedFrameworkInstallerFileRid Condition=" '$(IsDebianBaseDistro)' == 'true' OR '$(IsRPMBasedDistro)' == 'true' ">x64</SharedFrameworkInstallerFileRid>
+      <SharedFrameworkInstallerFileRid Condition=" '$(IsDebianBaseDistro)' == 'true' OR '$(IsRPMBasedDistro)' == 'true' ">$(Architecture)</SharedFrameworkInstallerFileRid>
 
       <!-- Use the "x64" Rid when downloading Linux runtime dependencies Debian package. -->
       <RuntimeDepsInstallerFileRid>$(CoreSetupRid)</RuntimeDepsInstallerFileRid>
-      <RuntimeDepsInstallerFileRid Condition=" '$(IsDebianBaseDistro)' == 'true' ">x64</RuntimeDepsInstallerFileRid>
+      <RuntimeDepsInstallerFileRid Condition=" '$(IsDebianBaseDistro)' == 'true' ">$(Architecture)</RuntimeDepsInstallerFileRid>
 
       <AlternateArchitecture Condition="'$(Architecture)' == 'x86'">x64</AlternateArchitecture>
       <AlternateArchitecture Condition="'$(Architecture)' == 'x64'">x86</AlternateArchitecture>

src/redist/targets/GetRuntimeInformation.targets

@@ -13,7 +13,6 @@
       <OSName Condition=" '$(OSName)' == '' AND '$(IsLinux)' == 'True' ">linux</OSName>
       <OSPlatform Condition=" '$(OSPlatform)' == '' AND '$(IsLinux)' == 'True' ">linux</OSPlatform>
 
-      <Architecture Condition=" '$(Architecture)' == '' ">x64</Architecture>
       <Rid Condition=" '$(Rid)' == '' ">$(OSName)-$(Architecture)</Rid>
     </PropertyGroup>