uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

pkgs/build-support/setup-hooks/separate-debug-info.sh

@@ -0,0 +1,43 @@
+export NIX_SET_BUILD_ID=1
+export NIX_LDFLAGS+=" --compress-debug-sections=zlib"
+export NIX_CFLAGS_COMPILE+=" -ggdb -Wa,--compress-debug-sections"
+dontStrip=1
+
+fixupOutputHooks+=(_separateDebugInfo)
+
+_separateDebugInfo() {
+    [ -e "$prefix" ] || return 0
+
+    local dst="${debug:-$out}"
+    if [ "$prefix" = "$dst" ]; then return 0; fi
+
+    dst="$dst/lib/debug/.build-id"
+
+    # Find executables and dynamic libraries.
+    local i
+    while IFS= read -r -d $'\0' i; do
+        if ! isELF "$i"; then continue; fi
+
+        # Extract the Build ID. FIXME: there's probably a cleaner way.
+        local id="$($READELF -n "$i" | sed 's/.*Build ID: \([0-9a-f]*\).*/\1/; t; d')"
+        if [ "${#id}" != 40 ]; then
+            echo "could not find build ID of $i, skipping" >&2
+            continue
+        fi
+
+        # Extract the debug info.
+        header "separating debug info from $i (build ID $id)"
+        mkdir -p "$dst/${id:0:2}"
+
+        # This may fail, e.g. if the binary is for a different
+        # architecture than we're building for.  (This happens with
+        # firmware blobs in QEMU.)
+        (
+            $OBJCOPY --only-keep-debug "$i" "$dst/${id:0:2}/${id:2}.debug"
+            $STRIP --strip-debug "$i"
+
+            # Also a create a symlink <original-name>.debug.
+            ln -sfn ".build-id/${id:0:2}/${id:2}.debug" "$dst/../$(basename "$i")"
+        ) || rmdir -p "$dst/${id:0:2}"
+    done < <(find "$prefix" -type f -print0)
+}