test: Fix the test-scan-deps test for arm64ec

Add a separate arm64ec arch case, skip the x86_64 one.

test/test-scan-deps.cpp

@@ -20,7 +20,7 @@
 #include <version>
 
 // Test that we have set the expected architecture defines.
-#if defined(__x86_64__)
+#if defined(__x86_64__) && !defined(__arm64ec__)
 #ifndef EXPECT_x86_64
 #include <intentionally-missing-header>
 #endif
@@ -36,4 +36,8 @@
 #ifndef EXPECT_armv7
 #include <intentionally-missing-header>
 #endif
+#elif defined(__arm64ec__)
+#ifndef EXPECT_arm64ec
+#include <intentionally-missing-header>
+#endif
 #endif