Only build embedder unit tests for host builds (#9315)
Only build embedder unit tests for host builds (#9315)

Linux target builds for non-x86/x64 platforms were failing due to the
dependency on SwiftShader
chinmaygarde/sky_engine,tvolkert/engine,cdotstout/sky_engine,chinmaygarde/sky_engine,jason-simmons/flutter_engine,jason-simmons/flutter_engine,flutter/engine,mikejurka/engine,devoncarew/sky_engine,jason-simmons/flutter_engine,jamesr/flutter_engine,jamesr/flutter_engine,aam/engine,jason-simmons/sky_engine,rmacnak-google/engine,rmacnak-google/engine,devoncarew/engine,mikejurka/engine,chinmaygarde/flutter_engine,jason-simmons/sky_engine,jason-simmons/flutter_engine,aam/engine,cdotstout/sky_engine,devoncarew/sky_engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,devoncarew/sky_engine,mikejurka/engine,rmacnak-google/engine,jamesr/flutter_engine,devoncarew/engine,chinmaygarde/flutter_engine,flutter/engine,Hixie/sky_engine,tvolkert/engine,jason-simmons/flutter_engine,tvolkert/engine,jason-simmons/sky_engine,jamesr/flutter_engine,mikejurka/engine,devoncarew/sky_engine,jamesr/sky_engine,flutter/engine,mikejurka/engine,rmacnak-google/engine,chinmaygarde/flutter_engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,devoncarew/sky_engine,tvolkert/engine,chinmaygarde/flutter_engine,cdotstout/sky_engine,jason-simmons/sky_engine,jamesr/sky_engine,jason-simmons/flutter_engine,flutter/engine,chinmaygarde/sky_engine,devoncarew/sky_engine,aam/engine,chinmaygarde/sky_engine,Hixie/sky_engine,tvolkert/engine,chinmaygarde/sky_engine,tvolkert/engine,Hixie/sky_engine,jamesr/flutter_engine,Hixie/sky_engine,jason-simmons/sky_engine,devoncarew/engine,jason-simmons/sky_engine,rmacnak-google/engine,jamesr/sky_engine,chinmaygarde/sky_engine,flutter/engine,flutter/engine,jason-simmons/sky_engine,mikejurka/engine,aam/engine,jamesr/flutter_engine,jamesr/sky_engine,rmacnak-google/engine,mikejurka/engine,jamesr/sky_engine,chinmaygarde/flutter_engine,jamesr/sky_engine,tvolkert/engine,aam/engine,devoncarew/engine,jason-simmons/flutter_engine,flutter/engine,devoncarew/engine,mikejurka/engine,devoncarew/sky_engine,cdotstout/sky_engine,mikejurka/engine,Hixie/sky_engine,jamesr/sky_engine,flutter/engine,aam/engine,jamesr/flutter_engine,Hixie/sky_engine,cdotstout/sky_engine,Hixie/sky_engine,jamesr/flutter_engine,Hixie/sky_engine,chinmaygarde/sky_engine,jason-simmons/flutter_engine,aam/engine,rmacnak-google/engine,aam/engine,jamesr/flutter_engine,devoncarew/engine,devoncarew/engine