only run release builds on tags that start with "vX" (#4219)

.appveyor.yml

@@ -68,5 +68,5 @@ build_script:
 
       pushd . && cd tests && go mod tidy && go mod download && popd
 
-      if defined APPVEYOR_REPO_TAG_NAME ( dotnet msbuild /t:ReleaseProcess /v:Detailed build.proj )
+      .\scripts\release.cmd
 test: off

.travis.yml

@@ -1,4 +1,4 @@
-if: branch = master OR branch =~ ^features/ OR branch =~ ^feature- OR tag IS present
+if: branch = master OR branch =~ ^features/ OR branch =~ ^feature- OR tag =~ ^v\d+.*
 matrix:
   include:
   - os: linux

scripts/release.cmd

@@ -0,0 +1,6 @@
+echo %APPVEYOR_REPO_TAG_NAME%|findstr "^v[0-9]" >Nul 2>&1
+if %errorlevel% == 0 ( 
+dotnet msbuild /t:ReleaseProcess /v:Detailed build.proj
+) else (
+exit 0
+)