blowfish failure to compile

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

I've noticed the following failure in XenServer's build environment

> make[6]: Leaving directory
> '/builddir/build/BUILD/xen-4.19.1/tools/tests/x86_emulator'
> In file included from /usr/include/features.h:535,
>                  from /usr/include/bits/libc-header-start.h:33,
>                  from /usr/include/stdint.h:26,
>                  from
> /usr/lib/gcc/x86_64-xenserver-linux/12/include/stdint.h:9,
>                  from blowfish.c:18:
> /usr/include/gnu/stubs.h:7:11: fatal error: gnu/stubs-32.h: No such
> file or directory
>     7 | # include <gnu/stubs-32.h>
>       |           ^~~~~~~~~~~~~~~~
> compilation terminated.
> make[6]: *** [testcase.mk:15: blowfish.bin] Error 1

It's non-fatal, but it reduces the content in test_x86_emulator which we
do care about running.

Elsewhere in the tree we fix this with -ffreestanding -nostdinc
-I$(XEN_ROOT)/tools/firmware/include but that isn't an option for
test_x86_emulator in general which is hosted.

However, it is an option for blowfish.c specifically which is
freestanding, and for which we build a 32bit form in an otherwise 64bit
build.

Therefore, it stands to reason that:

diff --git a/tools/tests/x86_emulator/Makefile
b/tools/tests/x86_emulator/Makefile
index 294d27ebaa08..e46fd8becb96 100644
--- a/tools/tests/x86_emulator/Makefile
+++ b/tools/tests/x86_emulator/Makefile
@@ -33,8 +33,8 @@ HOSTCFLAGS += -m32 -I..
 
 else
 
-blowfish-cflags := ""
-blowfish-cflags-x86_32 := "-mno-accumulate-outgoing-args -Dstatic="
+blowfish-cflags := "-ffreestanding -nostdinc
-I$(XEN_ROOT)/tools/firmware/include "
+blowfish-cflags-x86_32 := "$(blowfish-cflags)
-mno-accumulate-outgoing-args -Dstatic="
 
 3dnow-vecs := 8
 3dnow-ints :=

should do what we want, except it doesn't.  Somehow this is getting
injected the intermediate blowfish.h:

> blowfish.h:617:99: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
> ‘__attribute__’ before ‘/’ token
>   617 | static const unsigned int __attribute__((section(".test,
> \"ax\", @progbits #")))
> blowfish_x86_32_I/local/xen.spec/scm/tools/tests/x86_emulator/../../../tools/firmware/include[]
> = {
>      
> |                                                                             
>                      
> ^

and at this point I've got completely lost in this build system.  The .h
generation seems to loop over each cflag, and while that looks plausible
for vector generation, I can't see how it works (except by accident) for
blowfish.

The problem is the generation of $flavor, but this logic is completely
opaque.

~Andrew