Index: .github/workflows/build.yml
===================================================================
diff -u -N -r0b679a9471f41bc2ba02372f3677e84fae7ba238 -r0129b8b89f86bcd559a2d1e296db8c32086770ec
--- .github/workflows/build.yml	(.../build.yml)	(revision 0b679a9471f41bc2ba02372f3677e84fae7ba238)
+++ .github/workflows/build.yml	(.../build.yml)	(revision 0129b8b89f86bcd559a2d1e296db8c32086770ec)
@@ -29,15 +29,15 @@
             tcltag: core-8-6-branch
             experimental: [true]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: trunk
             experimental: [true]
           - os: ubuntu-latest
             compiler: clang-12
             tcltag: trunk
             experimental: [true]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-6-branch
             experimental: [true]
           - os: ubuntu-latest
@@ -53,11 +53,11 @@
             tcltag: core-8-5-branch
             experimental: [true]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-branch
             experimental: [true]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-5-branch
             experimental: [true]
           - os: macos-latest
@@ -73,15 +73,15 @@
             tcltag: core-8-7-a5
             experimental: [false]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-5-19
             experimental: [false]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-6-12
             experimental: [false]
           - os: ubuntu-latest
-            compiler: gcc-11
+            compiler: gcc-10
             tcltag: core-8-7-a5
             experimental: [false]
     defaults: