Fix build for FreeBSD

[hselasky]

FYI: These two chunks were needed in order to use this program under FreeBSD.

--- meson.build.orig	2022-02-11 10:51:29 UTC
+++ meson.build
@@ -17,6 +17,7 @@ dep_jack = dependency('jack')
 dep_alsa = dependency('alsa')
 lib_dl = cc.find_library('dl')
 lib_pthread = cc.find_library('pthread')
+lib_execinfo = cc.find_library('execinfo')
 deps_a2jmidid = [dep_alsa, dep_jack, lib_dl, lib_pthread]
 
 # source definitions
@@ -50,6 +51,7 @@ if get_option('disable-dbus')
 else
   dep_dbus = dependency('dbus-1')
   deps_a2jmidid += [dep_dbus]
+  deps_a2jmidid += [lib_execinfo]
   dbus_data = configuration_data()
   dbus_data.set('bindir', join_paths(get_option('prefix'), get_option('bindir')))
   dbus_data.set('dbus_service_dir', join_paths(get_option('prefix'), 'share', 'dbus-1', 'services'))
--- sigsegv.c.orig	2022-02-11 10:51:46 UTC
+++ sigsegv.c
@@ -91,7 +91,7 @@ static void signal_segv(int signum, siginfo_t* info, v
     a2j_error("info.si_errno = %d", info->si_errno);
     a2j_error("info.si_code  = %d (%s)", info->si_code, si_codes[info->si_code]);
     a2j_error("info.si_addr  = %p", info->si_addr);
-#if !defined(__alpha__) && !defined(__ia64__) && !defined(__FreeBSD_kernel__) && !defined(__arm__) && !defined(__hppa__) && !defined(__sh__) && !defined(__aarch64__)
+#if !defined(__alpha__) && !defined(__ia64__) && !defined(__FreeBSD__) && !defined(__arm__) && !defined(__hppa__) && !defined(__sh__) && !defined(__aarch64__)
     for(i = 0; i < NGREG; i++)
         a2j_error("reg[%02d]       = 0x" REGFORMAT, i,
 #if defined(__powerpc__) && !defined(__powerpc64__)