Bump gcc 6 to 7 (#30903)

* Bump gcc 6 to 7

* Update

* Update 2

src/cpp/README.md

@@ -30,10 +30,10 @@ Therefore, gRPC supports several major build systems, which should satisfy most
 
 | Operating System | Architectures | Versions | Support Level |
 |------------------|---------------|----------|---------------|
-| Linux - Debian, Ubuntu, CentOS | x86, x64      | clang 6+, GCC 6.3+     | Officially Supported |
+| Linux - Debian, Ubuntu, CentOS | x86, x64      | clang 6+, GCC 7.3+     | Officially Supported |
 | Windows 10+                    | x86, x64      | Visual Studio 2017+    | Officially Supported |
 | MacOS                          | x86, x64      | XCode 12+              | Officially Supported |
-| Linux - Others                 | x86, x64      | clang 6+, GCC 6.3+     | Best Effort          |
+| Linux - Others                 | x86, x64      | clang 6+, GCC 7.3+     | Best Effort          |
 | Linux                          | ARM           |                        | Best Effort          |
 | iOS                            |               |                        | Best Effort          |
 | Android                        |               |                        | Best Effort          |

templates/tools/dockerfile/test/cxx_gcc_7_x64/Dockerfile.template

@@ -14,11 +14,12 @@
   # See the License for the specific language governing permissions and
   # limitations under the License.
   
-  FROM gcc:6
+  FROM gcc:7
   
   RUN apt-get update && apt-get install -y curl git time wget zip && apt-get clean
   <%include file="../../run_tests_python_deps.include"/>
-  <%include file="../../cmake_jessie_backports.include"/>
+  <%include file="../../cmake.include"/>
+  <%include file="../../ccache.include"/>
   <%include file="../../run_tests_addons.include"/>
 
   # Define the default command.

tools/dockerfile/test/cxx_gcc_7_x64/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM gcc:6
+FROM gcc:7
 
 RUN apt-get update && apt-get install -y curl git time wget zip && apt-get clean
 #====================
@@ -41,13 +41,24 @@ RUN python3 -m pip install --upgrade google-auth==1.23.0 google-api-python-clien
 
 
 #=================
-# Use cmake 3.6 from jessie-backports
-# should only be used for images based on debian jessie.
+# Install cmake
+# Note that this step should be only used for distributions that have new enough cmake to satisfy gRPC's cmake version requirement.
 
-RUN echo "deb http://archive.debian.org/debian jessie-backports main" | tee /etc/apt/sources.list.d/jessie-backports.list
-RUN echo 'Acquire::Check-Valid-Until "false";' > /etc/apt/apt.conf
-RUN sed -i '/deb http:\/\/deb.debian.org\/debian jessie-updates main/d' /etc/apt/sources.list
-RUN apt-get update && apt-get install -t jessie-backports -y cmake && apt-get clean
+RUN apt-get update && apt-get install -y cmake && apt-get clean
+
+#=================
+# Install ccache
+
+# Install ccache from source since ccache 3.x packaged with most linux distributions
+# does not support Redis backend for caching.
+RUN curl -sSL -o ccache.tar.gz https://github.com/ccache/ccache/releases/download/v4.5.1/ccache-4.5.1.tar.gz \
+    && tar -zxf ccache.tar.gz \
+    && cd ccache-4.5.1 \
+    && mkdir build && cd build \
+    && cmake -DCMAKE_BUILD_TYPE=Release -DZSTD_FROM_INTERNET=ON -DHIREDIS_FROM_INTERNET=ON .. \
+    && make -j4 && make install \
+    && cd ../.. \
+    && rm -rf ccache-4.5.1 ccache.tar.gz
 
 
 RUN mkdir /var/local/jenkins

tools/run_tests/run_tests.py

@@ -477,8 +477,8 @@ class CLanguage(object):
 
         if compiler == 'default' or compiler == 'cmake':
             return ('debian11', [])
-        elif compiler == 'gcc6':
-            return ('gcc_6', [])
+        elif compiler == 'gcc7':
+            return ('gcc_7', [])
         elif compiler == 'gcc10.2':
             return ('debian11', [])
         elif compiler == 'gcc10.2_openssl102':
@@ -1485,7 +1485,7 @@ argp.add_argument(
     '--compiler',
     choices=[
         'default',
-        'gcc6',
+        'gcc7',
         'gcc10.2',
         'gcc10.2_openssl102',
         'gcc12',

tools/run_tests/run_tests_matrix.py

@@ -300,7 +300,7 @@ def _create_portability_test_jobs(extra_args=[],
 
     # portability C and C++ on x64
     for compiler in [
-            'gcc6', 'gcc10.2_openssl102', 'gcc12', 'gcc_musl', 'clang6',
+            'gcc7', 'gcc10.2_openssl102', 'gcc12', 'gcc_musl', 'clang6',
             'clang13'
     ]:
         test_jobs += _generate_jobs(languages=['c', 'c++'],