Update CI Linux builds to use GCC 10

GCC 8 doesn't support C++17's parallel algorithms, which I'd like to
use, and GCC 10 is the newest major version available from Ubuntu
20.04's repositories.

This commit removes a Linux-only std::filesystem::path constructor test,
which fails due to a thrown exception when compiled with GCC 10. The
failure isn't important, because libloot avoids that particular
constructor: in a sense an exception is a bit better because it would
make any usage more obvious.

.github/workflows/ci.yml

@@ -100,13 +100,13 @@ jobs:
             language-pack-el \
             language-pack-tr \
             libicu-dev \
-            g++-8
+            g++-10
 
       - name: Run CMake
         run: |
           mkdir build
           cd build
-          export CXX="g++-8" CC="gcc-8"
+          export CXX="g++-10" CC="gcc-10"
           cmake .. -DBOOST_ROOT="boost_1_78_0" -DCPACK_PACKAGE_VERSION="${{ steps.get-libloot-version.outputs.version }}"
           make all
 

.github/workflows/release.yml

@@ -67,13 +67,13 @@ jobs:
             language-pack-el \
             language-pack-tr \
             libicu-dev \
-            g++-8
+            g++-10
 
       - name: Run CMake
         run: |
           mkdir build
           cd build
-          export CXX="g++-8" CC="gcc-8"
+          export CXX="g++-10" CC="gcc-10"
           cmake .. -DBOOST_ROOT="boost_1_78_0" -DCPACK_PACKAGE_VERSION="${{ needs.create_release.outputs.git_tag }}"
           make all