lm-sensors: fix build with glibc

lm-sensors: fix build with glibc

The lm-sensors build was failing on glibc-based targets with:
  ld: cannot find -liconv: No such file or directory

which occurred because the upstream Makefile unconditionally links
against -liconv, but glibc has iconv functionality built-in and does not
provide a separate libiconv library.

I submitted the new patch upstream to fix this:
https://github.com/hramrach/lm-sensors/pull/14

This change is backward compatible based on my testing building
lm-sensors for x86/64 with glibc and again with musl after having
applied the patch.

Build system: x86/64
Build-tested: x86/64-glibc and x86/64
Run-tested: x86/64-glibc (Intel N150 based box)

Signed-off-by: John Audia <[email protected]>