CI: restore build on GCC 5

.github/workflows/ci.yml

@@ -33,6 +33,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
+          - gcc: "5"
           - gcc: "6"
           - gcc: "7"
             cxxflags: -fsanitize=leak -fno-sanitize-recover=all

README.md

@@ -85,7 +85,7 @@ ArduinoJson is a C++ JSON library for Arduino and IoT (Internet Of Things).
     * [Unit test coverage close to 100%](https://coveralls.io/github/bblanchon/ArduinoJson?branch=6.x)
     * Continuously tested on
         * [Visual Studio 2017, 2019, 2022](https://ci.appveyor.com/project/bblanchon/arduinojson/branch/6.x)
-        * [GCC 6, 7, 8, 9, 10, 11](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
+        * [GCC 5, 6, 7, 8, 9, 10, 11](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
         * [Clang 3.8, 3.9, 4.0, 5.0, 6.0, 7, 8, 9, 10](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
     * [Continuously fuzzed with Google OSS Fuzz](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:arduinojson)
     * Passes all default checks of [clang-tidy](https://releases.llvm.org/10.0.0/tools/clang/tools/extra/docs/clang-tidy/)

extras/tests/IntegrationTests/CMakeLists.txt

@@ -9,7 +9,7 @@ add_executable(IntegrationTests
 	openweathermap.cpp
 )
 
-if(CMAKE_CXX_COMPILER_ID MATCHES "GNU")
+if(CMAKE_CXX_COMPILER_ID MATCHES "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 6)
 	target_compile_options(IntegrationTests
 		PUBLIC
 			-fsingle-precision-constant # issue 544