fix github-ci environments

.github/workflows/coverage.yml

@@ -4,7 +4,7 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: macos-10.15
+    runs-on: macos-11
     name: "coverage"
     steps:
     - uses: actions/checkout@v2

.github/workflows/darwin.yml

@@ -10,9 +10,9 @@ jobs:
       matrix:
         config:
         # https://github.com/actions/virtual-environments/tree/main/images/macos
-        - { os: "macos-10.15", xcode: "10.3" }
-        - { os: "macos-10.15", xcode: "11.7" }
-        - { os: "macos-10.15", xcode: "12.4" }
+        - { os: "macos-11", xcode: "13.0" }
+        - { os: "macos-11", xcode: "13.1" }
+        - { os: "macos-11", xcode: "13.2" }
     name: "xcode-${{matrix.config.xcode}}"
     steps:
     - uses: actions/checkout@v2

.github/workflows/linux.yml

@@ -10,13 +10,7 @@ jobs:
       matrix:
         config:
         # https://github.com/actions/virtual-environments/tree/main/images/linux
-        - { os: "ubuntu-20.04", cc: "gcc-7", cxx: "g++-7" }
-        - { os: "ubuntu-20.04", cc: "gcc-8", cxx: "g++-8" }
-        - { os: "ubuntu-20.04", cc: "gcc-9", cxx: "g++-9" }
         - { os: "ubuntu-20.04", cc: "gcc-10", cxx: "g++-10" }
-        - { os: "ubuntu-20.04", cc: "clang-7", cxx: "clang++-7" }
-        - { os: "ubuntu-20.04", cc: "clang-8", cxx: "clang++-8" }
-        - { os: "ubuntu-20.04", cc: "clang-9", cxx: "clang++-9" }
         - { os: "ubuntu-20.04", cc: "clang-10", cxx: "clang++-10" }
     name: "${{matrix.config.cxx}}"
     steps:

.github/workflows/windows.yml

@@ -10,8 +10,6 @@ jobs:
       matrix:
         config:
         # https://github.com/actions/virtual-environments/tree/main/images/win
-        - { os: "windows-2016", vs: "Visual Studio 2017", arch: "x86" }
-        - { os: "windows-2016", vs: "Visual Studio 2017", arch: "x64" }
         - { os: "windows-2019", vs: "Visual Studio 2019", arch: "x86" }
         - { os: "windows-2019", vs: "Visual Studio 2019", arch: "x64" }
     name: "${{matrix.config.vs}} ${{matrix.config.arch}}"

README.md

@@ -27,9 +27,10 @@
 
 ## Requirements
 
-- [gcc](https://www.gnu.org/software/gcc/) **>= 7**
-- [clang](https://clang.llvm.org/) **>= 7**
-- [msvc](https://visualstudio.microsoft.com/) **>= 2017**
+- [clang](https://clang.llvm.org/) **>= 10**
+- [gcc](https://www.gnu.org/software/gcc/) **>= 10**
+- [msvc](https://visualstudio.microsoft.com/) **>= 2019**
+- [xcode](https://developer.apple.com/xcode/) **>= 13.0**
 
 ## Installation