imx-mkimage: fix compilation issue for nativesdk builds

The '-fmacro-prefix' option is a new GCC option introduced in gcc version 8.

To keep compatibility with previous GCC versions, remove this option from
the DEBUG_PREFIX_MAP list so nativesdk builds are able to compile this recipe.

Following is the compilation issue avoided by this patch:

| gcc: error: unrecognized command line option ‘-fmacro-prefix-map=<yocto-workspace>/tmp/work/x86_64-nativesdk-deysdk-linux/nativesdk-imx-mkimage/git-r0=/usr/src/debug/nativesdk-imx-mkimage/git-r0’

Signed-off-by: Gonzalo Ruiz <Gonzalo.Ruiz@digi.com>

meta-digi-arm/recipes-bsp/imx-mkimage/imx-mkimage_git.bb

@@ -8,6 +8,11 @@ LICENSE = "GPLv2"
 LIC_FILES_CHKSUM = "file://${COREBASE}/meta/files/common-licenses/GPL-2.0;md5=801f80980d171dd6425610833a22dbe6"
 SECTION = "BSP"
 
+# Beware: applied last to first
+DEBUG_PREFIX_MAP = "-fdebug-prefix-map=${WORKDIR}=/usr/src/debug/${PN}/${EXTENDPE}${PV}-${PR} \
+                    -fdebug-prefix-map=${STAGING_DIR_HOST}= \
+                    -fdebug-prefix-map=${STAGING_DIR_NATIVE}= \
+"
 CFLAGS = "-O2 -Wall -std=c99 -I ${STAGING_INCDIR} -L ${STAGING_LIBDIR}"
 
 REV_CHIP ?= "B0"