RFR: 7904098: Allow experimental ASM build in the JCov build

[Alexandre Iline]

This change allows an arbitrary ASM build to be used.

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Commit messages:
 - CODETOOLS-7904098: Allow experimental ASM build in the JCov build

Changes: https://git.openjdk.org/jcov/pull/67/files
  Webrev: https://webrevs.openjdk.org/?repo=jcov&pr=67&range=00
  Issue: https://bugs.openjdk.org/browse/CODETOOLS-7904098
  Stats: 30 lines in 1 file changed: 22 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jcov/pull/67.diff
  Fetch: git fetch https://git.openjdk.org/jcov.git pull/67/head:pull/67

PR: https://git.openjdk.org/jcov/pull/67