openssl: add option to provide the openssl path

Add a new variable to have the directory that contains the openssl
libraries and headers needed for xtest. The build system will look
for the needed libraries and headers specified in this variable
during the compilation of xtest.

Signed-off-by: Davidson Kumaresan <davidson.kumaresan@arm.com>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Etienne Carriere <etienne.carriere@foss.st.com>

host/xtest/Makefile

@@ -40,6 +40,10 @@ endef
 WITH_OPENSSL ?= y
 ifeq ($(WITH_OPENSSL),y)
 CFLAGS += -DOPENSSL_FOUND=1 -DOPENSSL_API_COMPAT=10100
+ifneq ($(OPENSSL_INSTALL_PATH),)
+CFLAGS += -I$(OPENSSL_INSTALL_PATH)/include
+LDFLAGS += -L$(OPENSSL_INSTALL_PATH)/lib
+endif
 LDFLAGS += -lcrypto
 endif #require OpenSSL