[LoongArch] Fix '-mno-lsx' option not disabling LASX feature (#143821)

When '-march' with LASX feature and '-mno-lsx' options are used
together, '-mno-lsx' fails to disable LASX, leaving
'HasFeatureLASX=true' and causing incorrect '__loongarch_sx/asx=1' macro
definition.

Fixes loongson-community/discussions#95

(cherry picked from commit 2ecbfc0)

Author: Ami-zhang

clang/lib/Driver/ToolChains/Arch/LoongArch.cpp

@@ -253,6 +253,7 @@ void loongarch::getLoongArchTargetFeatures(const Driver &D,
         Features.push_back("+lsx");
     } else /*-mno-lsx*/ {
       Features.push_back("-lsx");
+      Features.push_back("-lasx");
     }
   }
 

clang/test/Preprocessor/init-loongarch.c

@@ -946,6 +946,10 @@
 // RUN:   | FileCheck --match-full-lines --check-prefix=MNO-LSX %s
 // RUN: %clang --target=loongarch64 -mno-lasx -mno-lsx -x c -E -dM %s -o - \
 // RUN:   | FileCheck --match-full-lines --check-prefix=MNO-LSX %s
+// RUN: %clang --target=loongarch64 -march=la464 -mno-lsx -x c -E -dM %s -o - \
+// RUN:   | FileCheck --match-full-lines --check-prefix=MNO-LSX %s
+// RUN: %clang --target=loongarch64 -mno-lsx -march=la464 -x c -E -dM %s -o - \
+// RUN:   | FileCheck --match-full-lines --check-prefix=MNO-LSX %s
 // MNO-LSX-NOT: #define __loongarch_asx
 // MNO-LSX-NOT: #define __loongarch_simd_width
 // MNO-LSX-NOT: #define __loongarch_sx