RFR: 8366777: Build fails unknown pseudo-op with old AS on linux-aarch64

[SendaoYan]

Hi all,

Build jdk on linux-aarch64 with older assembler version(as 2.30) will report compilation failre, shows as [JDK-8366777](https://bugs.openjdk.org/browse/JDK-8366777).

This PR add the expression `svfloat64_t a() {}` to makefile which will trigger the compilation during configure stage. After this PR, at configure stage will check the gcc and assember support `-march=armv8-a+sve` or not more comprehensive.

Testing:
- [x] On linux-aarch64 gcc12.3.1 as2.37, configure set SVE_CFLAGS as '-march=armv8-a+sve'
- [x] On linux-aarch64 gcc10.3.0 as2.30, configure set SVE_CFLAGS as empty


The compilation fails demo as below:


# cat sve.c 
#include <arm_sve.h>
svfloat64_t a() {}
# gcc -march=armv8-a+sve sve.c 
/tmp/ccVOzMzb.s: Assembler messages:
/tmp/ccVOzMzb.s:6: Error: unknown pseudo-op: `.variant_pcs'

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

Commit messages:
 - 8366777: Build fails unknown pseudo-op with old AS on linux-aarch64

Changes: https://git.openjdk.org/jdk/pull/27073/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27073&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366777
  Stats: 6 lines in 1 file changed: 3 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27073.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27073/head:pull/27073

PR: https://git.openjdk.org/jdk/pull/27073