RFR: 8264650: Cross-compilation to macos/aarch64 [v2]

[Anton Kozlov]

> Please review adding necessary flags for cross-compilation on macos/x86 targeting macos/aarch64.
> 
> All CFLAGS, CXXFLAGS, LDFLAGS need target CPU flag `-arch arm64`.
> This patch adds the flag along e.g `-m64`.
> 
> Tested:
> * cross-compilation 
>   * macos/x86 -> macos/aarch64: configure --openjdk-target=aarch64-apple-darwin
>   * macos/aarch64 -> macos/x86: configure --openjdk-target=x86_64-apple-darwin
> * native compilation:
>   * macos/aarch64
>   * macos/x86

Anton Kozlov has updated the pull request incrementally with one additional commit since the last revision:

  Add both ways cross-compilation

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3325/files
  - new: https://git.openjdk.java.net/jdk/pull/3325/files/3938a473..df62dd07

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3325&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3325&range=00-01

  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3325.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3325/head:pull/3325

PR: https://git.openjdk.java.net/jdk/pull/3325