kbuild: Move linker sciript check to prepare1

Same as the previous commit.
Move sanity check to prepare1 target to avoid nasty troubles.

Before this commit, LDSCRIPT existence was not checked
when it was specified by CONFIG_SYS_LDSCRIPT.
Now LDSCRIPT existence is checked for all boards.

$(wildcard $(LDSCRIPT)) must point to the linker scripts
with absolute path.
Otherwise, make will terminate with a false error
on out-of-tree build.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/Makefile b/Makefile
index 7b7c25a..0281171 100644
--- a/Makefile
+++ b/Makefile
@@ -495,7 +495,7 @@
 	#LDSCRIPT := $(TOPDIR)/board/$(BOARDDIR)/u-boot.lds.debug
 	ifdef CONFIG_SYS_LDSCRIPT
 		# need to strip off double quotes
-		LDSCRIPT := $(CONFIG_SYS_LDSCRIPT:"%"=%)
+		LDSCRIPT := $(srctree)/$(CONFIG_SYS_LDSCRIPT:"%"=%)
 	endif
 endif
 
@@ -518,9 +518,6 @@
 		# We don't expect a Makefile here
 		LDSCRIPT_MAKEFILE_DIR =
 	endif
-	ifeq ($(wildcard $(LDSCRIPT)),)
-$(error could not find linker script)
-	endif
 endif
 
 else
@@ -996,6 +993,10 @@
 	@/bin/false
 endif
 endif
+ifeq ($(wildcard $(LDSCRIPT)),)
+	@echo >&2 "  Could not find linker script."
+	@/bin/false
+endif
 
 archprepare: prepare1 scripts_basic