Fix target_vendor in non-idf Xtensa ESP32 targets

The Xtensa ESP32 targets are the following:
- xtensa-esp32-none-elf
- xtensa-esp32-espidf
- xtensa-esp32s2-none-elf
- xtensa-esp32s2-espidf
- xtensa-esp32s3-none-elf
- xtensa-esp32s3-espidf

The ESP-IDF targets already set `target_vendor="espressif"`, however,
the ESP32 is produced by Espressif regardless of whether using the IDF
or not, so we should set the target vendor there as well.

compiler/rustc_target/src/spec/targets/xtensa_esp32_none_elf.rs

@@ -15,6 +15,7 @@ pub(crate) fn target() -> Target {
         },
 
         options: TargetOptions {
+            vendor: "espressif".into(),
             cpu: "esp32".into(),
             linker: Some("xtensa-esp32-elf-gcc".into()),
             max_atomic_width: Some(32),

compiler/rustc_target/src/spec/targets/xtensa_esp32s2_none_elf.rs

@@ -15,6 +15,7 @@ pub(crate) fn target() -> Target {
         },
 
         options: TargetOptions {
+            vendor: "espressif".into(),
             cpu: "esp32-s2".into(),
             linker: Some("xtensa-esp32s2-elf-gcc".into()),
             max_atomic_width: Some(32),

compiler/rustc_target/src/spec/targets/xtensa_esp32s3_none_elf.rs

@@ -15,6 +15,7 @@ pub(crate) fn target() -> Target {
         },
 
         options: TargetOptions {
+            vendor: "espressif".into(),
             cpu: "esp32-s3".into(),
             linker: Some("xtensa-esp32s3-elf-gcc".into()),
             max_atomic_width: Some(32),