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=c3d8c6ac7e457bbde72ce54cd4caf4b9610e2d99'>root</a>/<a href='/guix/log/etc?id=c3d8c6ac7e457bbde72ce54cd4caf4b9610e2d99'>etc</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/etc?id=c3d8c6ac7e457bbde72ce54cd4caf4b9610e2d99&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-11-06 00:04:11 +0100'>2018-11-06</span></td><td><a href='/guix/commit/etc?id=aa919fbc890c5438166083f9ff02e4b1968a182b'>maint: Move substitute public keys to etc/substitutes.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-11-06 00:04:11 +0100'>2018-11-06</span></td><td><a href='/guix/commit/etc?id=7082873ea2771ebef900333e0fa7468d6395f330'>bash completion: Restore completion of available packages for 'guix build'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-10-14 23:48:49 +0200'>2018-10-14</span></td><td><a href='/guix/commit/etc?id=2510bd87562bfee9d82348f1c08dd78ccea12dd1'>guix-install.sh: Recognize armhf-linux.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-10-10 17:33:42 +0200'>2018-10-10</span></td><td><a href='/guix/commit/etc?id=d634db9401ac320383d45e24431442259cf6a2a4'>etc: Use git-file-name if origin is git-fetch.</a><span class='msg-avail'>...</span></td><td>Pierre Neidhardt</td></tr>
<tr><td><span title='2018-07-13 12:45:11 +0530'>2018-07-13</span></td><td><a href='/guix/commit/etc?id=9286c2950494b110e12d58d4ebd693d614120afe'>etc: snippets: Add guix-commit-message-use-https-home-page.</a><span class='msg-avail'>...</span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2018-07-13 09:27:31 +0530'>2018-07-13</span></td><td><a href='/guix/commit/etc?id=202befb4ae775cfdab1566f4a69ec184406a56be'>etc: snippets: Add new build systems to package snippet.</a><span class='msg-avail'>...</span></td><td>Arun Isaac</td></tr>
<tr><td><span title='2018-07-03 06:58:51 +0300'>2018-07-03</span></td><td><a href='/guix/commit/etc?id=3a15d0aa9c55881ddc3a21570350a743c28a6c92'>bash completion: Complete files names after 'guix weather -m'.</a><span class='msg-avail'>...</span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2018-07-03 06:58:51 +0300'>2018-07-03</span></td><td><a href='/guix/commit/etc?id=9b0a755f642542dd96065ad05ec9d844d8077fd7'>bash completion: Complete files names after 'guix build -L'.</a><span class='msg-avail'>...</span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2018-06-16 21:23:11 +0300'>2018-06-16</span></td><td><a href='/guix/commit/etc?id=bba0fa2499eefab02cacfed9958dc498abfd484d'>Add guix-daemon Bash completion file.</a><span class='msg-avail'>...</span></td><td>Oleg Pykhalov</td></tr>
<tr><td><span title='2018-05-19 22:47:07 +0200'>2018-05-19</span></td><td><a href='/guix/commit/etc?id=593fe736674fadedd961c499e5758fa9c96a57aa'>guix-install.sh: Fix chk_require exiting without warning.</a><span class='msg-avail'>...</span></td><td>Maxim Cournoyer</td></tr>