RFR: Improve and modernize the makefile [v2]

Mon Mar 15 19:57:27 UTC 2021

> A bunch of fixes to the make file, to use more modern/robust syntax, and to keep intermediate build results.
> 
> This is a prerequisite for any further changes to the make file.

Magnus Ihse Bursie has updated the pull request incrementally with one additional commit since the last revision:

  Additional improvements for reusability and debuggability

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

Changes:
  - all: https://git.openjdk.java.net/guide/pull/46/files
  - new: https://git.openjdk.java.net/guide/pull/46/files/e92b21f7..f4a03bd9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=guide&pr=46&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=guide&pr=46&range=00-01

  Stats: 55 lines in 1 file changed: 42 ins; 3 del; 10 mod
  Patch: https://git.openjdk.java.net/guide/pull/46.diff
  Fetch: git fetch https://git.openjdk.java.net/guide pull/46/head:pull/46

PR: https://git.openjdk.java.net/guide/pull/46