JavaScript Backend: testsuite: fix gmake errors

Several tests in !9133 (merged) fail due to gmake. For example:

gmake: *** [Makefile:7: T15261a] Error 1

we've disabled these tests, but this is the tracking ticket for the fix.

Check these off as you re-enable them:

T15261a: requires support for -with-rtsopts="-t -s" and +RTS --info
T15261b: requires support for +RTS --info
T16318: !10150 (closed)
T17648: JS backend doesn't compute exact CafInfos (HasNoCafRefs)
T20214: !10150 (closed)
T21336c: bad handling of setFinalizerExceptionHandler
rtsopts002: requires support for -with-rtsopts="--info", -with-rtsopts="-C0", and GHCRTS environment variable
withRtsOpts: requires support for -with-rtsopts="--info" and -with-rtsopts="-t"

Edited Mar 21, 2023 by Sylvain Henry

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