Align Kconfig and Kbuild logic to Linux 4.19 release with minimal impact
on files outside of this scope.

Our previous Kconfig sync was done by commit 5972ff07 ("kconfig /
kbuild: re-sync with Linux 4.18").

In this particular re-sync in order to keep clang support working a
number of related changes needed to be pulled in that had been missed
previously.  Not all of these changes we easily traceable and so have
been omitted from the list below.

The imported Linux commits are:
[From prior to v4.18]
9f3f1fd29976 kbuild: Add __cc-option macro
d7f14c66c273 kbuild: Enable Large File Support for hostprogs
6d79a7b424a5 kbuild: suppress warnings from 'getconf LFS_*'
24403874316a Shared library support
86a9df597cdd kbuild: fix linker feature test macros when cross compiling with Clang
0294e6f4a000 kbuild: simplify ld-option implementation

[From v4.18 to v4.19]
96f14fe738b6 kbuild: Rename HOSTCFLAGS to KBUILD_HOSTCFLAGS
10844aebf448 kbuild: Rename HOSTCXXFLAGS to KBU...