rust: patch bilge-impl to allow compilation with 1.63.0

Apply a patch that removes "let ... else" constructs, replacing them with
"if let ... else" or "let ... = match ...".  "let ... else" was stabilized in
Rust 1.65.0.

Reviewed-by: Junjie Mao <junjie.mao@hotmail.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

.gitattributes

@@ -5,3 +5,5 @@
 *.rs            diff=rust
 *.rs.inc        diff=rust
 Cargo.lock      diff=toml merge=binary
+
+*.patch         -text -whitespace

subprojects/bilge-impl-0.2-rs.wrap

@@ -5,3 +5,4 @@ source_filename = bilge-impl-0.2.0.tar.gz
 source_hash = feb11e002038ad243af39c2068c8a72bcf147acf05025dcdb916fcc000adb2d8
 #method = cargo
 patch_directory = bilge-impl-0.2-rs
+diff_files = bilge-impl-1.63.0.patch

subprojects/packagefiles/bilge-impl-1.63.0.patch

@@ -0,0 +1,45 @@
+--- a/src/shared/discriminant_assigner.rs
++++ b/src/shared/discriminant_assigner.rs
+@@ -26,20 +26,20 @@
+         let discriminant_expr = &discriminant.1;
+         let variant_name = &variant.ident;
+ 
+-        let Expr::Lit(ExprLit { lit: Lit::Int(int), .. }) = discriminant_expr else {
++        if let Expr::Lit(ExprLit { lit: Lit::Int(int), .. }) = discriminant_expr {
++            let discriminant_value: u128 = int.base10_parse().unwrap_or_else(unreachable);
++            if discriminant_value > self.max_value() {
++                abort!(variant, "Value of variant exceeds the given number of bits")
++            }
++
++            Some(discriminant_value)
++        } else {
+             abort!(
+                 discriminant_expr,
+                 "variant `{}` is not a number", variant_name;
+                 help = "only literal integers currently supported"
+             )
+-        };
+-
+-        let discriminant_value: u128 = int.base10_parse().unwrap_or_else(unreachable);
+-        if discriminant_value > self.max_value() {
+-            abort!(variant, "Value of variant exceeds the given number of bits")
+         }
+-
+-        Some(discriminant_value)
+     }
+ 
+     fn assign(&mut self, variant: &Variant) -> u128 {
+--- a/src/shared/fallback.rs
++++ b/src/shared/fallback.rs
+@@ -22,8 +22,9 @@
+             }
+             Unnamed(fields) => {
+                 let variant_fields = fields.unnamed.iter();
+-                let Ok(fallback_value) = variant_fields.exactly_one() else {
+-                    abort!(variant, "fallback variant must have exactly one field"; help = "use only one field or change to a unit variant")
++                let fallback_value = match variant_fields.exactly_one() {
++                    Ok(ok) => ok,
++                    _ => abort!(variant, "fallback variant must have exactly one field"; help = "use only one field or change to a unit variant")
+                 };
+ 
+                 if !is_last_variant {