[PATCH lvm2] acinclude.m4: Link when trying CCFLAGS

Through a build failure of LVM2 on musl-libc 1.2.5 in the Buildroot
autobuild service[1], I noticed that musl-libc's Scrt1 for microblaze
produces a relocation targeting the .text section, which subsequently
leads to a crash at run-time because musl-libc does not support
textrels[2]. Buildroot uses the "-z text" linker option to catch
textrels early, on musl-libc.

The error can be reduced to the following test case:

  $ cat hello.c
  #include <stdio.h>
  int main(void) { puts("Hello world!"); return 0; }
  $ host/bin/microblaze-buildroot-linux-musl-gcc hello.c -z text -pie -fPI=
C
  microblaze-buildroot-linux-musl/bin/ld: microblaze-buildroot-linux-musl/=
sysroot/lib/Scrt1.o:
    warning: relocation against `_start_c' in read-only section `.text'
  microblaze-buildroot-linux-musl/bin/ld: read-only segment has dynamic re=
locations
  collect2: error: ld returned 1 exit status

LVM2 uses -pie only after the AC_TRY_CCFLAG macro has determined that it
can be used. This is where the problem begins: AC_TRY_CCFLAG only tries
compiling, it does not try linking the resulting object file.

To catch problems like this, this patch changes AC_TRY_CCFLAG to link in
addition to compiling. By detecting correctly that -pie does not work on
musl-libc/microblaze with -ztext, the build failure in Buildroot is fixed.

[1]: http://autobuild.buildroot.net/results/dc4/dc4fc33eaeafe5d6707d26a373=
560402533954f6/build-end.log
[2]: https://www.openwall.com/lists/musl/2020/09/25/4

Signed-off-by: J. Neusch=C3=A4fer <[email protected]>
=2D--
Hi, I'm cross-posting this to the LVM2, Buildroot, and musl mailing
lists to get potential feedback early on.
=2D--
 acinclude.m4 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/acinclude.m4 b/acinclude.m4
index 47fdd59c3..9b1d3a605 100644
=2D-- a/acinclude.m4
+++ b/acinclude.m4
@@ -25,7 +25,7 @@ AC_DEFUN([AC_TRY_CCFLAG],
     ac_save_CFLAGS=3D$CFLAGS
     CFLAGS=3D$1
     AC_CACHE_CHECK([whether $CC accepts $1 flag], [ac_cv_flag_$2],
-	[AC_COMPILE_IFELSE([AC_LANG_PROGRAM()],
+	[AC_LINK_IFELSE([AC_LANG_PROGRAM()],
 			   [AS_VAR_SET([ac_cv_flag_$2], [yes])],
 			   [AS_VAR_SET([ac_cv_flag_$2], [no])])])
     CFLAGS=3D$ac_save_CFLAGS

=2D--
base-commit: 90a845a7087478a7cdc7a60d89d2e7ee1366160e
change-id: 20240811-microblaze-8ff8a6217471

Best regards,
=2D-
J. Neusch=C3=A4fer <[email protected]>