package/archlinux: lcov doesn't seem to get fixed anytime soon.

Using it with GCC 6, that produces correct output.

package/archlinux/PKGBUILD-coverage

@@ -6,7 +6,7 @@ pkgdesc="C++11/C++14 graphics middleware for games and data visualization (cover
 arch=('i686' 'x86_64')
 url="http://magnum.graphics"
 license=('MIT')
-depends=('corrade' 'openal' 'freeglut' 'sdl2' 'glfw')
+depends=('corrade' 'openal' 'freeglut' 'sdl2' 'glfw' 'gcc6')
 makedepends=('cmake' 'ninja' 'lcov')
 options=('!strip')
 provides=('magnum-git')
@@ -22,6 +22,7 @@ build() {
     export CXXFLAGS="$newcxxflags"
 
     cmake .. \
+        -DCMAKE_CXX_COMPILER="g++-6" \
         -DCMAKE_CXX_FLAGS="--coverage" \
         -DCMAKE_BUILD_TYPE=Debug \
         -DCMAKE_INSTALL_PREFIX=/usr \
@@ -70,11 +71,11 @@ check() {
 
     rm -rf coverage
     mkdir coverage
-    lcov --directory . --capture --output-file coverage.info
-    lcov --extract coverage.info "*/src/Magnum*/*" --output-file coverage.info
-    lcov --remove coverage.info "*/src/MagnumExternal/*" --output-file coverage.info
-    lcov --remove coverage.info "*/Test/*" --output-file coverage.info
-    lcov --remove coverage.info "*/build-coverage/src/*" --output-file coverage.info
+    lcov --gcov-tool="gcov-6" --directory . --capture --output-file coverage.info
+    lcov --gcov-tool="gcov-6" --extract coverage.info "*/src/Magnum*/*" --output-file coverage.info
+    lcov --gcov-tool="gcov-6" --remove coverage.info "*/src/MagnumExternal/*" --output-file coverage.info
+    lcov --gcov-tool="gcov-6" --remove coverage.info "*/Test/*" --output-file coverage.info
+    lcov --gcov-tool="gcov-6" --remove coverage.info "*/build-coverage/src/*" --output-file coverage.info
     genhtml --output-directory ./coverage coverage.info
 }