Update the Abseil minumum GCC version to GCC 7, which is

the earliest supported GCC version according to
https://github.com/google/oss-policies-info/blob/main/foundational-cxx-support-matrix.md

PiperOrigin-RevId: 503337021
Change-Id: Ibc7b2453b7aa30779b76e2a4ad918e39d0efcabe

absl/base/policy_checks.h

@@ -50,11 +50,11 @@
 #error "This package requires Visual Studio 2017 (MSVC++ 15.0) or higher."
 #endif
 
-// We support gcc 5 and later.
+// We support GCC 7 and later.
 // This minimum will go up.
 #if defined(__GNUC__) && !defined(__clang__)
-#if __GNUC__ < 5
-#error "This package requires gcc 5 or higher."
+#if __GNUC__ < 7
+#error "This package requires GCC 7 or higher."
 #endif
 #endif
 

ci/linux_docker_containers.sh

@@ -18,4 +18,4 @@
 readonly LINUX_ALPINE_CONTAINER="gcr.io/google.com/absl-177019/alpine:20201026"
 readonly LINUX_CLANG_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20220217"
 readonly LINUX_GCC_LATEST_CONTAINER="gcr.io/google.com/absl-177019/linux_hybrid-latest:20220217"
-readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20220621"
+readonly LINUX_GCC_FLOOR_CONTAINER="gcr.io/google.com/absl-177019/linux_gcc-floor:20230120"