[jdk11u-dev] RFR: 8239708: Split basics.m4 into basic.m4 and util.m4

[George Adams]

The main conflict is the lack of the WSL backport ([8215445: Enable building for Windows in WSL](https://github.com/openjdk/jdk/commit/46eb26b692ac7f9431d5b479028ec87e56707557)) Something which doesn't apply particularly cleanly and isn't required to achieve the MSYS2 backport that I'm trying to reach.

This backport will also considerably help many build/toolchain backports going forwards as this one nearly always trips me up when I backport patches.

This backport will allow me to more easily backport [8257679: Improved unix compatibility layer in Windows build (winenv)](https://github.com/openjdk/jdk/commit/d29c78da).

@RealCLanger / @GoeLin I suggest that this is run through the full SAP nightlies before this is merged.

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Commit messages:
 - Backport 63f939636a5fe9871f5f9057c93ed5b1a9924265

Changes: https://git.openjdk.org/jdk11u-dev/pull/1277/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1277&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8239708
  Stats: 4129 lines in 20 files changed: 2087 ins; 1906 del; 136 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1277.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1277/head:pull/1277

PR: https://git.openjdk.org/jdk11u-dev/pull/1277