SPARK-5669 [BUILD] Spark assembly includes incompatibly licensed libgfortran, libgcc code via JBLAS

Exclude libgfortran, libgcc bundled by JBLAS for Windows. This much is simple, and solves the essential license issue. But the more important question is whether MLlib works on Windows then.

Author: Sean Owen <sowen@cloudera.com>

Closes #4453 from srowen/SPARK-5669 and squashes the following commits:

734dd86 [Sean Owen] Exclude libgfortran, libgcc bundled by JBLAS, affecting Windows / OS X / Linux 32-bit (not Linux 64-bit)

assembly/pom.xml

@@ -114,6 +114,16 @@
                 <exclude>META-INF/*.RSA</exclude>
               </excludes>
             </filter>
+            <filter>
+              <!-- Exclude libgfortran, libgcc for license issues -->
+              <artifact>org.jblas:jblas</artifact>
+              <excludes>
+                <!-- Linux amd64 is OK; not statically linked -->
+                <exclude>lib/Linux/i386/**</exclude>
+                <exclude>lib/Mac OS X/**</exclude>
+                <exclude>lib/Windows/**</exclude>
+              </excludes>
+            </filter>
           </filters>
         </configuration>
         <executions>