qcacld-3.0: Kbuild: Update WLAN_CFG_OVERRIDE handling

Currently Kbuild handles WLAN_CONFIG_OVERRIDE directives by writing
the overrides into a file and then including the file. This violates
one of the requirements of the Hermetic Build feature which forbids
modifying the source directory. This is also subject to a race
condition where multiple concurrent builds attempt to write to the
file in parallel, and one of the builds ends up consuming the
overrides from both builds.

To avoid these issues update the WLAN_CFG_OVERRIDE handling to no
longer use a file, but to instead just $(eval) the overrides.

Change-Id: Iac159228a82b0a8134e272ce63ed568050e8e6ae
CRs-Fixed: 2917351

Kbuild

@@ -36,16 +36,9 @@ endif
 include $(WLAN_ROOT)/configs/$(CONFIG_QCA_CLD_WLAN_PROFILE)_defconfig
 
 # add configurations in WLAN_CFG_OVERRIDE
-ifneq ($(WLAN_CFG_OVERRIDE),)
-WLAN_CFG_OVERRIDE_FILE := $(WLAN_ROOT)/.wlan_cfg_override
-$(shell echo > $(WLAN_CFG_OVERRIDE_FILE))
-
 $(foreach cfg, $(WLAN_CFG_OVERRIDE), \
-	$(shell echo $(cfg) >> $(WLAN_CFG_OVERRIDE_FILE)))
-
-include $(WLAN_CFG_OVERRIDE_FILE)
-$(warning "Overriding WLAN config with: $(shell cat $(WLAN_CFG_OVERRIDE_FILE))")
-endif
+	$(eval $(cfg)) \
+	$(warning "Overriding WLAN config with: $(cfg)"))
 
 # This is temp change until connection manager changes for LFR2 are done.
 # Once LFR2 changes are done, CONFIG_CM_ENABLE will be removed and all