sd-boot: Add assert implementation

There is a ASSERT() macro from gnu-efi, but that does not show any
output to ConOut. Having to do some additional setup just to get
some debug output is tedious and outright difficult on real hardware.

src/boot/efi/assert.c

@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#ifndef NDEBUG
+
+#include <efi.h>
+#include <efilib.h>
+#include "util.h"
+
+void efi_assert(const char *expr, const char *file, unsigned line, const char *function) {
+      log_error_stall(L"systemd-boot assertion '%a' failed at %a:%u, function %a(). Halting.", expr, file, line, function);
+      for (;;)
+            uefi_call_wrapper(BS->Stall, 1, 60 * 1000 * 1000);
+}
+
+#endif

src/boot/efi/meson.build

@@ -17,6 +17,7 @@ efi_headers = files('''
 '''.split())
 
 common_sources = '''
+        assert.c
         disk.c
         graphics.c
         measure.c
@@ -219,12 +220,16 @@ if have_gnu_efi
                 compile_args += ['-Werror']
         endif
         if get_option('buildtype') == 'debug'
-                compile_args += ['-ggdb', '-O0']
+                compile_args += ['-ggdb', '-O0', '-DEFI_DEBUG']
         elif get_option('buildtype') == 'debugoptimized'
-                compile_args += ['-ggdb', '-Og']
+                compile_args += ['-ggdb', '-Og', '-DEFI_DEBUG']
         else
                 compile_args += ['-O2']
         endif
+        if get_option('b_ndebug') == 'true' or (
+           get_option('b_ndebug') == 'if-release' and ['plain', 'release'].contains(get_option('buildtype')))
+                compile_args += ['-DNDEBUG']
+        endif
 
         efi_ldflags = ['-T', efi_lds,
                        '-shared',