Schemas are not generated properly

[cpichard]

Describe the bug
When we build the schemas with scons and using the custom usdGenSchema, the install fails every 2 runs with the following error:

Flattening schema...
Install file: "build\windows_x86_64\msvc_opt\usd-0.22.11_arnold-7.2.4.0\schemas\source\generatedSchema.usda" as "install\schema\usdArnold\resources\usdArnold\generatedSchema.usda"
scons: *** [install\schema\usdArnold\resources\usdArnold\generatedSchema.usda] build\windows_x86_64\msvc_opt\usd-0.22.11_arnold-7.2.4.0\schemas\source\generatedSchema.usda: No such file or directory
scons: building terminated because of errors.

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-14021