Merge pull request #391 from omajid/system-library-libunwind

Introduce a UseSystemLibraries option to use the system libunwind

Author: weshaggard

dir.props

@@ -8,6 +8,7 @@
     <_IsBootstrapping Condition="'$(BootstrapBuildToolsDir)' != ''">true</_IsBootstrapping>
 
     <PortableBuild Condition="'$(PortableBuild)' == ''">false</PortableBuild>
+    <UseSystemLibraries Condition="'$(UseSystemLibraries)' == ''">true</UseSystemLibraries>
   </PropertyGroup>
 
   <PropertyGroup>

repos/coreclr.proj

@@ -4,6 +4,7 @@
   <PropertyGroup>
     <BuildArguments>$(Platform) $(Configuration) skiptests -PortableBuild=$(PortableBuild)</BuildArguments>
     <BuildArguments Condition="'$(OS)' != 'Windows_NT'">$(BuildArguments) msbuildonunsupportedplatform</BuildArguments>
+    <BuildArguments Condition="'$(UseSystemLibraries)' == 'true'">$(BuildArguments) cmakeargs -DCLR_CMAKE_USE_SYSTEM_LIBUNWIND=TRUE</BuildArguments>
     <BuildArguments Condition="$(Platform.Contains('arm'))">$(BuildArguments) skipnuget cross -skiprestore cmakeargs -DFEATURE_GDBJIT=TRUE</BuildArguments>
     <BuildCommand>$(ProjectDirectory)/build$(ShellExtension) $(BuildArguments) --</BuildCommand>
     <BuildCommand Condition="$(Platform.Contains('arm'))">$(ArmEnvironmentVariables) $(BuildCommand)</BuildCommand>