Update libffi to 3.4.6

Build failure on fedora 40:

    libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I.. -I. -I../include -Iinclude -I../src -Wall -fstack-protector-strong -fno-plt -O2 -fexceptions -MT src/types.lo -MD -MP -MF src/.deps/types.Tpo -c ../src/types.c -o src/types.o >/dev/null 2>&1
    ../src/tramp.c: In function 'ffi_tramp_get_temp_file':
    ../src/tramp.c:262:22: error: implicit declaration of function 'open_temp_exec_file' [-Wimplicit-function-declaration]
    262 |   tramp_globals.fd = open_temp_exec_file ();

Issue appears to have been fixed in 3.4.4, but bumping to .6 as that's
the most current.

configs/components/libffi.rb

@@ -1,6 +1,6 @@
 component 'libffi' do |pkg, settings, platform|
-  pkg.version '3.4.3'
-  pkg.md5sum 'b57b0ac1d1072681cee9148a417bd2ec'
+  pkg.version '3.4.6'
+  pkg.md5sum 'b9cac6c5997dca2b3787a59ede34e0eb'
   pkg.url "https://github.com/libffi/libffi/releases/download/v#{pkg.get_version}/#{pkg.get_name}-#{pkg.get_version}.tar.gz"
   pkg.mirror "#{settings[:buildsources_url]}/#{pkg.get_name}-#{pkg.get_version}.tar.gz"