RFR: 8294549: configure script should detect unsupported path [v2]

[Mike Duigou]

> The OpenJDK build system does not support building when the source code resides on a path that contains a space. This requirement is documented in the build instructions but not enforced by the configure script.
> 
> This change adds an explicit checks to the wrapper `configure` script that fail the build if the source code to be built is located in a directory who's path contains a space character or the build path cannot be determined.
> 
> Includes some idiom modernization and shell scripting best practices changes.

Mike Duigou has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains one additional commit since the last revision:

  8294549: configure script should detect unsupported path
  
  The OpenJDK build system does not support building when the source code
  resides on a path that contains a space. This requirement is documented in the
  build instructions but not enforced by the configure script.
  
  This change adds an explicit checks to the wrapper `configure` script that fail
  the build if the source code to be built is located in a directory who's path
  contains a space character or the build path cannot be determined.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10477/files
  - new: https://git.openjdk.org/jdk/pull/10477/files/6197cf42..85ae7cc0

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10477&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10477&range=00-01

  Stats: 238242 lines in 2971 files changed: 125727 ins; 73010 del; 39505 mod
  Patch: https://git.openjdk.org/jdk/pull/10477.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10477/head:pull/10477

PR: https://git.openjdk.org/jdk/pull/10477