Remove symbols that don't exist in musl from linker benchmark

The lseek64, lstat64, pread64 and pwrite64 symbols have been removed
from musl 1.2.4.

Bug: 286415000
Test: builds
Change-Id: Icba9e92e1ccbb5b52d6c60e554ab411c9e5c1954
diff --git a/benchmarks/linker_relocation/regen/gen_bench.py b/benchmarks/linker_relocation/regen/gen_bench.py
index 6533189..d34a9a9 100755
--- a/benchmarks/linker_relocation/regen/gen_bench.py
+++ b/benchmarks/linker_relocation/regen/gen_bench.py
@@ -115,9 +115,13 @@
     'getprogname',
     'gettid',
     'isnanf',
+    'lseek64',
+    'lstat64',
     'mallinfo',
     'malloc_info',
+    'pread64',
     'pthread_gettid_np',
+    'pwrite64',
     'res_mkquery',
     'strlcpy',
     'strtoll_l',