Update .travis.yml

.travis.yml

@@ -50,6 +50,16 @@ addons: &clang10
     sources:
       - sourceline: "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main"
         key_url: "https://apt.llvm.org/llvm-snapshot.gpg.key"
+        
+addons: &clang12
+  apt:
+    packages:
+      - clang-12
+      - lldb-12
+      - lld-12
+    sources:
+      - sourceline: "deb http://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main"
+        key_url: "https://apt.llvm.org/llvm-snapshot.gpg.key"        
 
 
 matrix:
@@ -89,8 +99,14 @@ matrix:
       os: linux
       dist: bionic
       addons: *clang10
+      
             
-
+    # Test clang-12.0: C++20, Build=Debug
+    - env: CLANG_VERSION=11 BUILD_TYPE=Debug CPP=20 ASAN=Off
+      os: linux
+      dist: bionic
+      addons: *clang12
+                        
 
 before_script:
   - if [ -n "$GCC_VERSION" ]; then export CXX="g++-${GCC_VERSION}" CC="gcc-${GCC_VERSION}"; fi