build: add missing openssl-devel package for centos-8 vpp-ext-deps

- In a new centos-8 installation, vpp-ext-deps fails on missing
  ssl.h header file after 'make install-deps'.

Type: fix

Signed-off-by: Dave Wallace <[email protected]>
Change-Id: I521d817dd1f1e21aff427d98b9832ea7c7b89339

Author: dwallacelf

Makefile

@@ -130,7 +130,7 @@ ifeq ($(OS_ID),fedora)
 	RPM_DEPENDS_GROUPS = 'C Development Tools and Libraries'
 else ifeq ($(OS_ID)-$(OS_VERSION_ID),centos-8)
 	RPM_DEPENDS += yum-utils
-	RPM_DEPENDS += compat-openssl10
+	RPM_DEPENDS += compat-openssl10 openssl-devel
 	RPM_DEPENDS += python2-devel python36-devel python3-ply
 	RPM_DEPENDS += python3-virtualenv python3-jsonschema
 	RPM_DEPENDS += cmake