(cmake): cmake configure appends spaces in compilation flags

What does this MR do?

• Strip cmake compilation flags on Windows
• Avoids cmake adding a space at the end of compilation flags

How to test it?

• launch cmake configure several times
• run ninja
• ninja doesn't have to rebuild all targets every time

Data

no required data

Some results

• Ninja mustn't rebuild what is already built

Additional tests to run

• Build on Windows

Associated issue

Closes #397 (closed)