build.yml: add solution file path

Author: JonnyOThan

.github/workflows/build.yml

@@ -14,3 +14,5 @@ on:
 jobs:
   build:
     uses: KSPModdingLibs/KSPBuildTools/.github/workflows/build.yml@main
+    with:
+      solution-file-path: KerbalVR_Mod/KerbalVR_Mod.sln