Constrain rake-compiler version to 0.9.4

[utkarsh2102]

Description

Constrain rake-compiler version to 0.9.4 to fix ClassNotFound exception when using MiniSSL with Java8.

Fixes: #2301

Signed-off-by: Utkarsh Gupta <utkarsh@debian.org>

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[utkarsh2102]

Pretty sure this failing check isn't related to this PR.
Here are Ruby issues about this:

• https://bugs.ruby-lang.org/issues/10978
• https://bugs.ruby-lang.org/issues/11223