Makefile, import/Make.defs: Fix undefined symbols for CONFIG_BUILD_KERNEL=y

Summary:
- I noticed that applications made by 'make import' contain
  undefined symbols such as printf for CONFIG_BUILD_KERNEL=y
- This commit fixes this issue by adding user libraries.
- Also, this commit generates libapps.a which is used for init

Impact:
- CONFIG_BUILD_KERNEL=y only

Testing:
- Build (mkimport, make import) with sama5d4-ek:knsh

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

import/Make.defs

@@ -74,6 +74,12 @@ else
   LDLIBPATH = -L $(TOPDIR)$(DELIM)libs
 endif
 
+# Link with user libraries
+
+ifeq ($(CONFIG_BUILD_KERNEL),y)
+  LDLIBS = -lapps -lxx -lmm -lc -lm -lproxies
+endif
+
 # Try to get the path to libgcc.a.  Of course, this only works for GCC
 # toolchains.