toolchain: prepare to pass more additional CFLAGS via the wrapper

Currently, we pass the user-supplied so-called target optimisation flags
to the wrapper.

We're going to have additional such CFLAGS to pass, so push-back the
formatting loop to quote the options at the last moment.

Reported-by: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: "Yann E. MORIN" <yann.morin@orange.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Cc: Thomas De Schampheleire <thomas.de_schampheleire@nokia.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
diff --git a/toolchain/toolchain-wrapper.mk b/toolchain/toolchain-wrapper.mk
index 613f5f6..c9e6fd3 100644
--- a/toolchain/toolchain-wrapper.mk
+++ b/toolchain/toolchain-wrapper.mk
@@ -16,11 +16,13 @@
 TOOLCHAIN_WRAPPER_ARGS = $($(PKG)_TOOLCHAIN_WRAPPER_ARGS)
 TOOLCHAIN_WRAPPER_ARGS += -DBR_SYSROOT='"$(STAGING_SUBDIR)"'
 
+TOOLCHAIN_WRAPPER_OPTS = \
+	$(call qstrip,$(BR2_TARGET_OPTIMIZATION))
+
 # We create a list like '"-mfoo", "-mbar", "-mbarfoo"' so that each flag is a
 # separate argument when used in execv() by the toolchain wrapper.
-TOOLCHAIN_WRAPPER_OPTS = \
-	$(foreach f,$(call qstrip,$(BR2_TARGET_OPTIMIZATION)),"$(f)"$(comma))
-TOOLCHAIN_WRAPPER_ARGS += -DBR_ADDITIONAL_CFLAGS='$(TOOLCHAIN_WRAPPER_OPTS)'
+TOOLCHAIN_WRAPPER_ARGS += \
+	-DBR_ADDITIONAL_CFLAGS='$(foreach f,$(TOOLCHAIN_WRAPPER_OPTS),"$(f)"$(comma))'
 
 ifeq ($(BR2_CCACHE),y)
 TOOLCHAIN_WRAPPER_ARGS += -DBR_CCACHE