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='2020-08-29 16:24:17 +0200'>2020-08-29</span></td><td><a href='/guix/commit/build-aux/pre-inst-env.in?id=d7965b58d25c9c7648ba5682223f32d759fdffda'>build: Remove references to the 'nix-hash' program.</a><span class='msg-avail'>...<span class='msg-tooltip'>* configure.ac: Remove check for 'nix-hash'.
* tests/base32.scm (%nix-hash, %have-nix-hash?): Remove.
("sha256 &amp; bytevector-&gt;nix-base32-string"): Remove test.
* build-aux/pre-inst-env.in: Do not set 'NIX_HASH' environment
variable.
</span></span></td><td>Ludovic Courtès</td></tr>