RFR: JEP 386 patch - minor cleanup [v2]

[Alexander Scherbatiy]

> "JEP 386 patch - minor cleanup" changes discussed on portola-dev alias:
> https://mail.openjdk.java.net/pipermail/portola-dev/2020-August/000471.html
> 
> Changed:
> * RELEASE_FILE_OS_LIBC is introduced in make files
> * glibc_version is renamed to libc_version
> * added fix for numa_node_to_cpus NUMA method
> * WhiteBox is used to check musl libc in tests
> * Platform.isBusybox(tool) method is added to check busybox in tests
> 
> Removed:
> * HOTSPOT_TARGET_LIBC flag
> * workaround for issues for execvp file call in childproc.c file
> * workaround for coredump issue in ps_core.c file
> 
> Skipped:
> * isnanf change from globalDefinitions_gcc.hpp
> * SIGRTMAX changes from NativeThread.c and linux_close.c files

Alexander Scherbatiy has updated the pull request with a new target base due to a merge or a rebase. The pull request
now contains 38 commits:

 - JEP 386 patch - Files.readSymbolicLink(toolpath) already checks that symlink exists
 - JEP 386 patch - Fix code formatting in ProcessBuilder/Basic.java
 - JEP 386 patch - Remove Basic.java dependency from  RedirectWithLongFilename.java
 - JEP 386 patch - Comment is made shorter in java_md.c
 - JEP 386 patch - Move numa_node_to_cpus function implementation to os_linux.cpp
 - JEP 386 patch - Make PaX related error message shorter
 - JEP 386 patch - Add LIBC CFLAG
 - JEP 386 patch - Remove unused fpu_control.h include from os_linux_aarch64.cpp
 - JEP 386 patch - Do not use WhiteBox in launcher tests
 - JEP 386 patch - Merge WhiteBox
 - ... and 28 more: https://git.openjdk.java.net/portola/compare/0e2f7b57...71c96ec8

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

Changes: https://git.openjdk.java.net/portola/pull/12/files
 Webrev: https://webrevs.openjdk.java.net/?repo=portola&pr=12&range=01
  Stats: 443 lines in 36 files changed: 142 ins; 195 del; 106 mod
  Patch: https://git.openjdk.java.net/portola/pull/12.diff
  Fetch: git fetch https://git.openjdk.java.net/portola pull/12/head:pull/12

PR: https://git.openjdk.java.net/portola/pull/12