[jdk11u-dev] RFR: 8299616: [11u] Bootcycle build fails after JDK-8257679 backport [v2]

[Aleksey Shipilev]

> Currently, JDK 11u `make bootcycle-images` fails with:
> 
> 
>  bootcycle-spec.gmk:32: *** non-numeric first argument to `word' function: ''. Stop.
> 
> 
> The apparent reason is [JDK-8257679](https://bugs.openjdk.org/browse/JDK-8257679) that did the following change:
>  https://github.com/openjdk/jdk11u-dev/commit/40f4fc2da8532252a1660c7f082eb19046f4bc70#diff-935527b393cb4625a8874febf5fe39d43479a2228ef437f4e104ba3001e1e30fL31-L40
> 
> Note that the left-over hunk uses `JAVA_EXEC_POS`, which is defined in the hunk that was removed. This PR reinstantiates that hunk.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `make bootcycle-images`
>  - [ ] Windows x86_64 fastdebug `make bootcycle-images`

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Fix comment order

-------------

Changes:
  - all: https://git.openjdk.org/jdk11u-dev/pull/1639/files
  - new: https://git.openjdk.org/jdk11u-dev/pull/1639/files/b0ad92ed..97b192f0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1639&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1639&range=00-01

  Stats: 4 lines in 1 file changed: 2 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1639.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1639/head:pull/1639

PR: https://git.openjdk.org/jdk11u-dev/pull/1639