.github/workflows/compilers.yml: more compilers

Added some cross compilers that we can run on GitHub Workflow runner
environments.  Because they are cross compilers we cannot run the
generated binary.  The added matrix are compile-only.

.github/workflows/compilers.yml

@@ -8,12 +8,13 @@ on: [push, pull_request]
 env:
   default_cc: clang-11
   append_cc: ''
+  crosshost: ''
 
   # -O1 is faster than -O3 in our tests... Majority of time are consumed trying
   # to optimize binaries.  Also Github Actions runs on a relatively modern CPU
   # compared to, say, GCC 4 or Clang 3.  We don't specify `-march=native`
   # because compilers tend not understand what the CPU is.
-  optflags: '-O1 -march=x86-64 -mtune=generic'
+  optflags: '-O1'
 
   # -g0 disables backtraces when SEGV.  Do not set that.
   debugflags: '-ggdb3'
@@ -64,6 +65,15 @@ jobs:
           - { key: default_cc, name: clang-4.0, value: clang-4.0 }
           - { key: default_cc, name: clang-3.9, value: clang-3.9 }
 
+          - { key: crosshost, name: aarch64-linux-gnu,     value: aarch64-linux-gnu }
+#         - { key: crosshost, name: arm-linux-gnueabi,     value: arm-linux-gnueabi }
+#         - { key: crosshost, name: arm-linux-gnueabihf,   value: arm-linux-gnueabihf }
+#         - { key: crosshost, name: i686-w64-mingw32,      value: i686-w64-mingw32 }
+#         - { key: crosshost, name: powerpc-linux-gnu,     value: powerpc-linux-gnu }
+          - { key: crosshost, name: powerpc64le-linux-gnu, value: powerpc64le-linux-gnu }
+          - { key: crosshost, name: s390x-linux-gnu,       value: s390x-linux-gnu }
+          - { key: crosshost, name: x86_64-w64-mingw32,    value: x86_64-w64-mingw32 }
+
           - { key: append_cc, name: c99,   value: '-std=c99   -Werror=pedantic -pedantic-errors' }
           - { key: append_cc, name: c11,   value: '-std=c11   -Werror=pedantic -pedantic-errors' }
           - { key: append_cc, name: c17,   value: '-std=c17   -Werror=pedantic -pedantic-errors' }
@@ -162,10 +172,19 @@ jobs:
       - name: Run configure
         working-directory: build
         run: |
-          ../src/configure -C \
-            ${default_configure} \
-            ${append_configure} \
-            --with-gcc="${default_cc} ${append_cc}"
+          if [ -n "${crosshost}" ]; then
+            ../src/configure -C \
+              ${default_configure} \
+              ${append_configure} \
+              --host="${crosshost}"
+          else
+            ../src/configure -C \
+              ${default_configure} \
+              ${append_configure} \
+              --with-gcc="${default_cc} ${append_cc}"
+          fi
+      - run: $make extract-extlibs
+        working-directory: build
       - run: $make incs
         working-directory: build
       - run: $make