ci: dump curl_config.h to log in all jobs

Also:
- GHA/windows: merge full and brief dump into a single job step.
- fix shellcheck warning 'useless cat'.

Closes #15266

.github/workflows/linux-old.yml

@@ -84,6 +84,11 @@ jobs:
           make install
           src/curl --disable --version
 
+      - name: 'cmake build-only curl_config.h'
+        run: |
+          echo '::group::raw'; cat bld-1/lib/curl_config.h || true; echo '::endgroup::'
+          grep -F '#define' bld-1/lib/curl_config.h | sort || true
+
       - name: 'cmake generate (out-of-tree, c-ares, libssh, zstd, gssapi)'
         run: |
           mkdir bld-cares
@@ -92,6 +97,11 @@ jobs:
             -DENABLE_ARES=ON -DCURL_ZSTD=ON -DCURL_USE_GSSAPI=ON -DCURL_USE_LIBSSH2=OFF -DCURL_USE_LIBSSH=ON -DUSE_LIBRTMP=ON \
             -DCURL_LIBCURL_VERSIONED_SYMBOLS=ON
 
+      - name: 'cmake curl_config.h'
+        run: |
+          echo '::group::raw'; cat bld-cares/lib/curl_config.h || true; echo '::endgroup::'
+          grep -F '#define' bld-cares/lib/curl_config.h | sort || true
+
       - name: 'cmake build'
         run: |
           make -C bld-cares
@@ -117,6 +127,11 @@ jobs:
             --with-openssl --enable-ares --with-libssh --with-zstd --with-gssapi --with-librtmp \
             --prefix="$PWD"/../install-am
 
+      - name: 'autoconf curl_config.h'
+        run: |
+          echo '::group::raw'; cat bld-am/lib/curl_config.h || true; echo '::endgroup::'
+          grep -F '#define' bld-am/lib/curl_config.h | sort || true
+
       - name: 'autoconf build'
         run: |
           make -C bld-am