RFR: 8304498: JShell does not switch to raw mode when there is no /bin/test [v2]

[Jan Lahoda]

> If JShell is run on a system that does not have `/bin/test` (which is, apparently, possible for some systems, which only have `/usr/bin/test`), it won't switch the terminal into the raw mode, and the input will not work properly.
> 
> The proposed fix herein is to detect whether `test` existing in `/usr/bin/test`, and if yes, use that location. Use the existing `/bin/test` otherwise.

Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:

  Checking the executable flags instead of running the program, as suggested.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13100/files
  - new: https://git.openjdk.org/jdk/pull/13100/files/159ef1a0..f7631210

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13100&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13100&range=00-01

  Stats: 9 lines in 1 file changed: 2 ins; 6 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/13100.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13100/head:pull/13100

PR: https://git.openjdk.org/jdk/pull/13100