[libc++abi] Fix lpStart adjustment for exceptions table (#72727)

When lpStartEncoding is different from DW_EH_PE_omit, lpStart can be set
to zero which is a valid base address for landing pads. Such base value
is useful when landing pads are placed in different sections.

Fixes #72582.

GitOrigin-RevId: 185302530847a28f44e48a67a79fd4eba048a1c7
2 files changed