Fix build failure when using Swig 4.

Taken from upstream:
https://github.com/fifengine/fifengine/commit/d14f232f4cd9a00b05d6872957070e8c020f515d

diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -893,7 +893,7 @@ if(build-python)
   find_package(PythonLibs ${PYTHON_VERSION_STRING} EXACT)
   include_directories(${PYTHON_INCLUDE_PATH})
 
-  set(CMAKE_SWIG_FLAGS -modern -fastdispatch -dirvtable -nosafecstrings -noproxydel -fastproxy -fastinit -fastunpack -fastquery -modernargs -nobuildnone -keyword -w511 -w473 -w404 -w314)
+  set(CMAKE_SWIG_FLAGS -modern -fastdispatch -dirvtable -noproxydel -fastproxy -fastinit -fastunpack -fastquery -modernargs -keyword -w511 -w473 -w404 -w314)
 
   set_source_files_properties("${PROJECT_BINARY_DIR}/fife.i" PROPERTIES CPLUSPLUS ON)
   set(FIFE_SOURCES ${FIFE_CORE_SRC})
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<div class='path'>path: <a href='/guix/log/?id=1962c6b286e36b8d5165a4992710f3132adb04c4'>root</a>/<a href='/guix/log/tests?id=1962c6b286e36b8d5165a4992710f3132adb04c4'>tests</a>/<a href='/guix/log/tests/openpgp.scm?id=1962c6b286e36b8d5165a4992710f3132adb04c4'>openpgp.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/openpgp.scm?id=1962c6b286e36b8d5165a4992710f3132adb04c4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-09-29 22:53:36 +0200'>2020-09-29</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=680b80e37453d4e23ad8188d60894916e1c07162'>openpgp: Fix argument order of 'fxbit-set?'.</a><span class='msg-avail'>...</span></td><td>Lars-Dominik Braun</td></tr>
<tr><td><span title='2020-05-04 09:56:13 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=b835e158d51c873a99367afd27f3d57cfe92e10e'>openpgp: Add 'string-&gt;openpgp-packet'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:13 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=bd8126558dc7a022d7853d803d7134ffa1b7bc52'>openpgp: 'lookup-key-by-{id,fingerprint}' return the key first.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:12 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=b45fa0a123bec8d023e5520dfb381bfc73313929'>openpgp: 'verify-openpgp-signature' looks up by fingerprint when possible.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:12 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=efe1f0122c61b8932671d07419f0200c170a994e'>openpgp: Add 'lookup-key-by-fingerprint'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:12 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=7b2b3a13cc2d9b043f37b2e7ba0f147c08de8fad'>openpgp: Store the issuer key id and fingerprint in &lt;openpgp-signature&gt;.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:12 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=4459c7859c286ab54fa3a9901c8a17591b04c516'>openpgp: Decode the issuer-fingerprint signature subpacket.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2020-05-04 09:56:12 +0200'>2020-05-04</span></td><td><a href='/guix/commit/tests/openpgp.scm?id=43408e304ffb1149f35cb539b40d673d567c9116'>Add (guix openpgp).</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>