/usr/src/gcc-4.9/debian/libgomp1.symbols is in gcc-4.9-source 4.9.3-13ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | libgomp.so.1 libgomp1 #MINVER#
#include "libgomp1.symbols.common"
GOMP_atomic_end@GOMP_1.0 4.2.1
GOMP_atomic_start@GOMP_1.0 4.2.1
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