python3: Fix native compilation of gdbm module and manifest

The gdbm module wasnt being built on python3-native showing the following
error during compilation:

Failed to build these modules:
_gdbm

This patch adds the required dependency to fix the compilation problem.

This issue on python3-native caused the manifest creation script to be
unaware of the gdbm library, so this patch also fixes the create_manifest
task for target python, and the manifest file to reflect the changes on
target python as well.

(From OE-Core rev: c47b54aeae5daabb458d6f7118a16257021c1822)

Signed-off-by: Alejandro Hernandez <alejandr@xilinx.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/python/python3/python3-manifest.json

@@ -366,7 +366,8 @@
     "db": {
         "cached": [],
         "files": [
-            "${libdir}/python3.5/dbm"
+            "${libdir}/python3.5/dbm",
+            "${libdir}/python3.5/lib-dynload/_dbm.*.so"
         ],
         "rdepends": [
             "core"
@@ -493,6 +494,16 @@
         ],
         "summary": "Python's fcntl interface"
     },
+    "gdbm": {
+        "cached": [],
+        "files": [
+            "${libdir}/python3.5/lib-dynload/_gdbm.*.so"
+        ],
+        "rdepends": [
+            "core"
+        ],
+        "summary": "Python GNU database support"
+    },
     "html": {
         "cached": [
             "${libdir}/python3.5/__pycache__/formatter.*.pyc"
@@ -1126,4 +1137,4 @@
         ],
         "summary": "Python XML-RPC support"
     }
-}
+}