CPP:Improve CMakeLists to not build a shared library when RE2 is used and not available as a shared library. Patch contributed by philip.liard
CPP:Improve CMakeLists to not build a shared library when RE2 is used and not available as a shared library. Patch contributed by philip.liard

weitzhandler/libphonenumber-csharp-1,caseykramer/libphonenumber-csharp,fengzhyuan/libphonenumber-csharp,jagui/libphonenumber-csharp,weitzhandler/libphonenumber-csharp-1,fengzhyuan/libphonenumber-csharp,weitzhandler/libphonenumber-csharp-1,weitzhandler/libphonenumber-csharp-1,weitzhandler/libphonenumber-csharp-1,jarroda/libphonenumber-dotnet,jagui/libphonenumber-csharp,caseykramer/libphonenumber-csharp,jarroda/libphonenumber-dotnet,caseykramer/libphonenumber-csharp,jarroda/libphonenumber-dotnet,fengzhyuan/libphonenumber-csharp,jarroda/libphonenumber-dotnet,caseykramer/libphonenumber-csharp,jarroda/libphonenumber-dotnet,caseykramer/libphonenumber-csharp,caseykramer/libphonenumber-csharp,jarroda/libphonenumber-dotnet,jagui/libphonenumber-csharp,jarroda/libphonenumber-dotnet,fengzhyuan/libphonenumber-csharp,weitzhandler/libphonenumber-csharp-1,fengzhyuan/libphonenumber-csharp,jagui/libphonenumber-csharp,jarroda/libphonenumber-dotnet,weitzhandler/libphonenumber-csharp-1,fengzhyuan/libphonenumber-csharp,fengzhyuan/libphonenumber-csharp,caseykramer/libphonenumber-csharp