objcopy prepends directory pathname to symbol name

I am tying to use objcopy to include a binary form of a text file into an executable. (At runtime I need the file as a string). This works fine until the linker needs to find the references from the symbol names. The problem is that objcopy prepends the symbol names with the pathname to the file. Since I am using GNU Autotools to ship the package this prepended pathname changes and I don't know what external linker symbol to use in the C/C++ program.

nm libtest.a |grep textfile
textfile.o:
00001d21 D _binary__home_git_textfile_end
00001d21 A _binary__home_git_textfile_size
00000000 D _binary__home_git_textfile_start

libtest.a was produced with (extract from Makefile.am):

SUFFIXES = .txt
.txt.$(OBJEXT):
    objcopy --input binary --output elf32-i386 --binary-architecture i386 $< $@

How can I tell objcopy to only us the stem of the filename as linker symbols? Or is there another way around the problem?