lib: descend into sub directories only when it is necessary

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>

Makefile

@@ -232,10 +232,10 @@ OBJS := $(addprefix $(obj),$(OBJS))
 HAVE_VENDOR_COMMON_LIB = $(if $(wildcard board/$(VENDOR)/common/Makefile),y,n)
 
 LIBS-y += lib/libgeneric.o
-LIBS-y += lib/rsa/librsa.o
-LIBS-y += lib/lzma/liblzma.o
-LIBS-y += lib/lzo/liblzo.o
-LIBS-y += lib/zlib/libz.o
+LIBS-$(CONFIG_RSA) += lib/rsa/librsa.o
+LIBS-$(CONFIG_LZMA) += lib/lzma/liblzma.o
+LIBS-$(CONFIG_LZO) += lib/lzo/liblzo.o
+LIBS-$(CONFIG_ZLIB) += lib/zlib/libz.o
 LIBS-$(CONFIG_TIZEN) += lib/tizen/libtizen.o
 LIBS-$(HAVE_VENDOR_COMMON_LIB) += board/$(VENDOR)/common/lib$(VENDOR).o
 LIBS-y += $(CPUDIR)/lib$(CPU).o

lib/lzma/Makefile

@@ -10,4 +10,4 @@
 
 CFLAGS += -D_LZMA_PROB32
 
-obj-$(CONFIG_LZMA) += LzmaDec.o LzmaTools.o
+obj-y += LzmaDec.o LzmaTools.o

lib/lzo/Makefile

@@ -5,4 +5,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_LZO) += lzo1x_decompress.o
+obj-y += lzo1x_decompress.o

lib/rsa/Makefile

@@ -7,6 +7,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-ifdef CONFIG_FIT_SIGNATURE
-obj-$(CONFIG_RSA) += rsa-verify.o
-endif
+obj-$(CONFIG_FIT_SIGNATURE) += rsa-verify.o

lib/zlib/Makefile

@@ -5,4 +5,4 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-obj-$(CONFIG_ZLIB) += zlib.o
+obj-y += zlib.o