RFR: 8304134 jib bootstrapper fails to quote filename when checking download filetype

[Ludvig Janiuk]

Add quoting not to fail on paths with spaces.

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Commit messages:
 - 8304134 jib bootstrapper fails to quote filename when checking download filetype

Changes: https://git.openjdk.org/jdk/pull/13138/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13138&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304134
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13138.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13138/head:pull/13138

PR: https://git.openjdk.org/jdk/pull/13138