CI: travis-ci: replace not defined SSL_LIB, SSL_INC for BotringSSL builds

after 73b520b958be4ee79b4f09a32d6718a13dc2d1fd variables SSL_LIB, SSL_INC
are not set, but still used by BoringSSL builds. That leads to error
(I wish we could stop on such errors) and using stock openssl instead
of boringssl
diff --git a/scripts/build-ssl.sh b/scripts/build-ssl.sh
index 34eee9b..9a6a2b2 100755
--- a/scripts/build-ssl.sh
+++ b/scripts/build-ssl.sh
@@ -103,14 +103,14 @@
 	cmake  -GNinja -DCMAKE_BUILD_TYPE=release -DBUILD_SHARED_LIBS=1 ..
 	ninja
 
-	rm -rf ${SSL_LIB} || exit 0
-	rm -rf ${SSL_INC} || exit 0
+	rm -rf ${HOME}/opt/lib || exit 0
+	rm -rf ${HOME}/opt/include || exit 0
 
-	mkdir -p ${SSL_LIB}
-	cp crypto/libcrypto.so ssl/libssl.so ${SSL_LIB}
+	mkdir -p ${HOME}/opt/lib
+	cp crypto/libcrypto.so ssl/libssl.so ${HOME}/opt/lib
 
-	mkdir -p ${SSL_INC}
-	cp -r ../include/* ${SSL_INC}
+	mkdir -p ${HOME}/opt/include
+	cp -r ../include/* ${HOME}/opt/include
 	)
 fi