ci: Add "it compiles" coverage for --with-static-compiler

Prep for further changes.

.github/workflows/tests.yml

@@ -209,6 +209,16 @@ jobs:
             configure-options: >-
               --with-soup3
 
+          # A build using static prepareorot
+          - name: Debian stable + static-prepareroot
+            image: debian:stable-slim
+            container-options: --security-opt seccomp=unconfined
+            pre-checkout-setup: |
+              apt-get update
+              apt-get install -y git
+            configure-options: >-
+              --with-static-compiler="gcc"
+
           # Ubuntu builds. Unfortunately, when the latest release is
           # also the latest LTS, latest and rolling are the same. Other
           # options would be to test the previous LTS by name or to test

Makefile-switchroot.am

@@ -46,6 +46,7 @@ ostree_boot_SCRIPTS += ostree-prepare-root
 
 ostree-prepare-root : $(ostree_prepare_root_SOURCES)
 	$(STATIC_COMPILER) -o $@ -static $(top_srcdir)/src/switchroot/ostree-prepare-root.c $(ostree_prepare_root_CPPFLAGS) $(AM_CFLAGS) $(DEFAULT_INCLUDES) -DOSTREE_PREPARE_ROOT_STATIC=1
+CLEANFILES += ostree-prepare-root
 else
 ostree_boot_PROGRAMS += ostree-prepare-root
 ostree_prepare_root_CFLAGS += $(AM_CFLAGS) -Isrc/switchroot -I$(srcdir)/composefs