Travis: use GCC 9 for coverage

.travis.yml

@@ -114,7 +114,11 @@ matrix:
               key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
           packages: ['clang-9']
       env: SCRIPT=test _CC=clang-9 _CXX=clang++-9
-    - env: SCRIPT=coverage
+    - addons:
+        apt:
+          sources: ['ubuntu-toolchain-r-test']
+          packages: ['g++-9']
+      env: SCRIPT=coverage _CC=gcc-9 _CXX=g++-9 GCOV=gcov-9
     - os: osx
       osx_image: xcode8.3
       env: SCRIPT=test

extras/CompileOptions.cmake

@@ -36,7 +36,7 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "(GNU|Clang)")
 endif()
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL  "GNU")
-	if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.8)
+	if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.8) AND (NOT ${COVERAGE}))
 		add_compile_options(-g -Og)
 	else()
 		add_compile_options(-g -O0)
@@ -70,15 +70,15 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
 endif()
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-	if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.0)
+	if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.0) AND (NOT ${COVERAGE}))
 		add_compile_options(-g -Og)
 	else()
 		add_compile_options(-g -O0)
 	endif()
 endif()
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "AppleClang")
-	if(CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 9.0)
+	if((CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 9.0) AND (NOT ${COVERAGE}))
 		add_compile_options(-g -Og)
 	else()
 		add_compile_options(-g -O0)

extras/ci/coverage.sh

@@ -1,9 +1,12 @@
 #!/bin/sh -eux
 
+export CC="$_CC"
+export CXX="$_CXX"
+
 cmake -DCOVERAGE=true .
 make 
 make test
 
 pip install --user cpp-coveralls 'requests[security]'
 pwd
-coveralls --include 'src' --gcov-options '\-lp'
+coveralls --include 'src' --gcov "$GCOV" --gcov-options '\-lp'