bootstrap: No need to disabled shared libraries

[imp]

Summary

There's no need to disable shared libraries when building the bootstrap
tools. This was added on 2000 (commit ad879ce9552c) when the perl
bootstrap was added (libperl and miniperl) and saved a fair amount of
time. However, these days we rarely build any libraries when
bootstrapping, so the optimization isn't all that much, and shared
libraries are more robust accross versions that static libraries due to
creaping dependencies. In addition, linux and macos have been building
like this for some time because static binaries on those systems are
difficult to impossible.

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