[8u] RFR: use gcc instead of ld to link genSocketOptionRegistry

[Alex Kashchenko]

Hi,

Please review the following fix for aarch32-8u crosscompile builds:

Webrev: 
http://cr.openjdk.java.net/~akasko/aarch32/jdk8u/jdk_genSocketOptionRegistry/webrev.00/

Without this change jdk build fails on linking genSocketOptionRegistry.

About the change:

  - it is used in aarch64-jdk8u [1]
  - it is not used upstream [2]
  - it is used in RHEL and Fedora on all platforms
  - it breaks Windows builds


[1] 
http://hg.openjdk.java.net/aarch64-port/jdk8u/jdk/file/fff403c14ad7/make/gensrc/GensrcMisc.gmk#l79
[2] 
http://hg.openjdk.java.net/jdk8u/jdk8u/jdk/file/652c6ab45018/make/gensrc/GensrcMisc.gmk#l79

-- 
-Alex