clang-tidy: Suppress warning about assignments in if statements

clang-tools 15.0.0 appears to have added a new warning that will always
complain about assignments in if statements, which we use in a number of
places in passt/pasta.  Encountered on Fedora 37 with
clang-tools-extra-15.0.0-3.fc37.x86_64.

Suppress the new warning so that we can compile and test.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Makefile

@@ -259,11 +259,16 @@ docs: README.md
 # - readability-identifier-length
 #	Complains about any identifier <3 characters, reasonable for
 #	globals, pointlessly verbose for locals and parameters.
+#
+# - bugprone-assignment-in-if-condition
+#	Dubious value over the compiler's built-in warning.  Would
+#	increase verbosity.
 
 clang-tidy: $(SRCS) $(HEADERS)
 	clang-tidy -checks=*,-modernize-*,\
 	-clang-analyzer-valist.Uninitialized,\
 	-cppcoreguidelines-init-variables,\
+	-bugprone-assignment-in-if-condition,\
 	-bugprone-macro-parentheses,\
 	-google-readability-braces-around-statements,\
 	-hicpp-braces-around-statements,\