The Hexagon driver only checked for an explicit -pie flag when
constructing the link command, ignoring the toolchain's PIE default. For
linux-musl targets, isPIEDefault() returns true (via the Linux toolchain
base class), so the compiler generates PIC/PIE code (-pic-level 2
-pic-is-pie) but the linker never received -pie.
This mismatch caused LTO failures: without -pie the linker sets
Reloc::Static for the LTO backend, which generates GP-relative
(small-data) references that lld cannot resolve.
Use hasFlag() to respect the toolchain default, and guard the -pie
emission against -shared and -r (relocatable) modes.
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