compiler: -Wmissing-include-dirs hardening

Warn if a user-supplied include directory does not exist.

This already surfaced a bug that is fixed by this commit.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

configure.ac

@@ -702,6 +702,7 @@ AX_CHECK_COMPILE_FLAG([-g], [CFLAGS="$CFLAGS -g"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([--mcet -fcf-protection], [CFLAGS="$CFLAGS --mcet -fcf-protection"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Werror=implicit-function-declaration], [CFLAGS="$CFLAGS -Werror=implicit-function-declaration"],,[-Werror])
 AX_CHECK_COMPILE_FLAG([-Wlogical-op], [CFLAGS="$CFLAGS -Wlogical-op"],,[-Werror])
+AX_CHECK_COMPILE_FLAG([-Wmissing-include-dirs], [CFLAGS="$CFLAGS -Wmissing-include-dirs"],,[-Werror])
 
 AX_CHECK_LINK_FLAG([-z relro], [LDLAGS="$LDLAGS -z relro"],,[])
 AX_CHECK_LINK_FLAG([-z now], [LDLAGS="$LDLAGS -z now"],,[])

src/tests/Makefile.am

@@ -48,7 +48,6 @@ AM_CFLAGS=-DLXCROOTFSMOUNT=\"$(LXCROOTFSMOUNT)\" \
 	  -DRUNTIME_PATH=\"$(RUNTIME_PATH)\" \
 	  -I $(top_srcdir)/src \
 	  -I $(top_srcdir)/src/lxc \
-	  -I $(top_srcdir)/src/lxc/bdev \
 	  -I $(top_srcdir)/src/lxc/cgroups \
 	  -I $(top_srcdir)/src/lxc/tools \
 	  -pthread