arm/edk2-firmware: clean up build invocation

Add some comments to make it clear what variables are being passed as
what arguments to build.

The build tool is on PATH, so there's no need to use an absolute path.

Change-Id: If9229d4927205e1b9a9a0bf7f7526e33006a03fd
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-bsp/uefi/edk2-firmware.inc

@@ -25,11 +25,14 @@ UPSTREAM_CHECK_GITTAGREGEX = "^edk2-stable(?P<pver>\d+)$"
 
 EDK2_BUILD_RELEASE = ""
 EDK2_PLATFORM      = ""
+# build --platform
 EDK2_PLATFORM_DSC  = ""
 EDK2_BIN_NAME      = ""
+# build --arch
 EDK2_ARCH          = ""
 
-EDK2_BUILD_MODE = "${@bb.utils.contains('EDK2_BUILD_RELEASE', '1', 'RELEASE', 'DEBUG', d)}"
+# build --buildtarget
+EDK2_BUILD_MODE ?= "${@bb.utils.contains('EDK2_BUILD_RELEASE', '1', 'RELEASE', 'DEBUG', d)}"
 
 # Baremetal, no need for a C library
 DEPENDS_remove = "virtual/${TARGET_PREFIX}compilerlibs virtual/libc"
@@ -72,11 +75,11 @@ do_compile() {
     oe_runmake -C ${S}/BaseTools
 
     PATH="${WORKSPACE}:${BTOOLS_PATH}:$PATH" \
-    "${S}/BaseTools/BinWrappers/PosixLike/build" \
-       -a "${EDK2_ARCH}" \
-       -b ${EDK2_BUILD_MODE} \
-       -t ${EDK_COMPILER} \
-       -p ${EDK2_PLATFORM_DSC}
+    build \
+       --arch "${EDK2_ARCH}" \
+       --buildtarget ${EDK2_BUILD_MODE} \
+       --tagname ${EDK_COMPILER} \
+       --platform ${EDK2_PLATFORM_DSC}
 }
 
 do_install() {