The firmware is cross-compiled, but the build system ends up using
'objcopy' instead of 'xtensa-elf-objcopy' by default.  Force it to
use the right one.

--- source/target_firmware/configure	2014-10-28 20:57:26.834436561 +0100
+++ source/target_firmware/configure	2014-10-28 20:57:29.666436530 +0100
@@ -11,6 +11,7 @@ mkdir -p build
 cat > "$TOOLCHAIN_FILE" <<EOF
 INCLUDE(CMakeForceCompiler)
 
+SET(CMAKE_OBJCOPY xtensa-elf-objcopy)
 SET(CMAKE_SYSTEM_PROCESSOR xtensa)
 SET(CMAKE_FIND_ROOT_PATH ${TOOLCHAIN}/$TARGET)
 SET(CMAKE_STRIP :)
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<tr><td><span title='2017-11-30 18:19:31 +0530'>2017-11-30</span></td><td><a href='/guix/commit/gnu/packages/direct-connect.scm?id=2b1a5ed854d3d373b960ef922eb71c52937263c0'>gnu: linuxdcpp: Use scons-build-system.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/direct-connect.scm (linuxdcpp): Switch to scons-build-system.
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<tr><td><span title='2017-05-06 02:26:03 +0530'>2017-05-06</span></td><td><a href='/guix/commit/gnu/packages/direct-connect.scm?id=99c1554c9ba1fd22d7dfdeba221088a3849ee27b'>gnu: Add linuxdcpp.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/direct-connect.scm (linuxdcpp): New variable.
</span></span></td><td>Arun Isaac</td></tr>