8244853: The static build of libextnet is missing the JNI_OnLoad_extnet function

Reviewed-by: alanb

src/jdk.net/linux/native/libextnet/LinuxSocketOptions.c

@@ -33,6 +33,11 @@
 #include "jni_util.h"
 #include "jdk_net_LinuxSocketOptions.h"
 
+/*
+ * Declare library specific JNI_Onload entry if static build
+ */
+DEF_STATIC_JNI_OnLoad
+
 /*
  * Class:     jdk_net_LinuxSocketOptions
  * Method:    setQuickAck

src/jdk.net/macosx/native/libextnet/MacOSXSocketOptions.c

@@ -32,6 +32,11 @@
 #include <netinet/in.h>
 #include "jni_util.h"
 
+/*
+ * Declare library specific JNI_Onload entry if static build
+ */
+DEF_STATIC_JNI_OnLoad
+
 static jint socketOptionSupported(jint sockopt) {
     jint one = 1;
     jint rv, s;

src/jdk.net/solaris/native/libextnet/SolarisSocketOptions.c

@@ -31,6 +31,11 @@ static jfieldID sf_bandwidth;
 
 static int initialized = 0;
 
+/*
+ * Declare library specific JNI_Onload entry if static build
+ */
+DEF_STATIC_JNI_OnLoad
+
 /*
  * Class:     jdk_net_SolarisSocketOptions
  * Method:    init