feat: drop CMake 3.6 and below, modernize CMake

fix: include PYTHON_IS_DEBUG

Author: henryiii

.github/workflows/ci.yml

@@ -95,7 +95,6 @@ jobs:
     - name: Configure C++11
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -163,7 +162,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -210,7 +208,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -256,7 +253,6 @@ jobs:
     - name: Configure
       shell: bash
       run: >
-        cmake --version &&
         cmake -S . -B build
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON

.github/workflows/configure.yml

@@ -34,33 +34,31 @@ jobs:
 
     - name: Make build directories
       run: |
-        mkdir build2.8
         mkdir build3.7
+        mkdir build3.11
         mkdir build3.18
 
-    - name: Setup CMake 2.8
+    - name: Setup CMake 3.7
       uses: jwlawson/[email protected]
       with:
-        cmake-version: 2.8
+        cmake-version: 3.7
 
-    - name: Configure 2.8
-      working-directory: build2.8
+    - name: Configure 3.7
+      working-directory: build3.7
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
         -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
 
-    - name: Setup CMake 3.7
+    - name: Setup CMake 3.11
       uses: jwlawson/[email protected]
       with:
-        cmake-version: 3.7
+        cmake-version: 3.11
 
-    - name: Configure 3.7
-      working-directory: build3.7
+    - name: Configure 3.11
+      working-directory: build3.11
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON
@@ -74,7 +72,6 @@ jobs:
     - name: Configure 3.18
       working-directory: build3.18
       run: >
-        cmake --version &&
         cmake ..
         -DPYBIND11_WERROR=ON
         -DDOWNLOAD_CATCH=ON