musl >= 1.2.4 only defines lseek64 and friends if _LARGEFILE64_SOURCE is
defined.  This causes the symbol check to "succeed" but compilation to
later fail.

--- llvm-14.0.6.src/cmake/config-ix.cmake.old	2022-06-22 11:46:24.000000000 -0500
+++ llvm-14.0.6.src/cmake/config-ix.cmake	2023-05-05 21:36:46.662084291 -0500
@@ -250,9 +250,7 @@
 if( HAVE_SIGNAL_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*" AND NOT APPLE )
   check_symbol_exists(sigaltstack signal.h HAVE_SIGALTSTACK)
 endif()
-set(CMAKE_REQUIRED_DEFINITIONS "-D_LARGEFILE64_SOURCE")
 check_symbol_exists(lseek64 "sys/types.h;unistd.h" HAVE_LSEEK64)
-set(CMAKE_REQUIRED_DEFINITIONS "")
 check_symbol_exists(mallctl malloc_np.h HAVE_MALLCTL)
 check_symbol_exists(mallinfo malloc.h HAVE_MALLINFO)
 check_symbol_exists(mallinfo2 malloc.h HAVE_MALLINFO2)