Do not build with -Winline

-Winline causes architecture- and optimization-dependent build failures
due to -Werror.  -Winline warns about inlining decisions based on
branch hints, in effect preventing the use of inline functions in
header files (because they might be called on unlikely branches, leading
to a decision not to inline).

The option was apparently added to the glibc build at a time when GCC
did not support the always_inline attribute.  With current GCC versions,
inlining failure for functions declared always_inline will receive a
warning under -Wattributes, which is enabled by default, so -Winline
appears unnecessary.