build: remove -mretpoline and NO_EXTRA_CFLAGS

The -mretpoline flag is not documented in the current versions of gcc
and clang and it is what causes scan-build to fail:

    $ ./configure CC=clang | grep retpoline
    checking whether C compiler accepts -mretpoline... yes
       EXTRA_CFLAGS:  -mretpoline -fstack-clash-protection -fstack-protector-strong
    $ scan-build --status-bugs make
    scan-build: Using '/usr/bin/clang-15' for static analysis
    make -C src/lib
    make[1]: Entering directory '/tmp/firejail/src/lib'
    /usr/bin/../lib/clang/ccc-analyzer [...] -mretpoline [...] -c common.c -o common.o
    gcc: error: unrecognized command-line option ‘-mretpoline’
    make[1]: *** [../../src/prog.mk:16: common.o] Error 1
    make[1]: Leaving directory '/tmp/firejail/src/lib'
    make: *** [Makefile:59: src/lib] Error 2
    scan-build: Analysis run complete.
    scan-build: Removing directory '/tmp/scan-build-[...]' because it contains no reports.
    scan-build: No bugs found.

Environment: clang 15.0.7-9 and gcc 13.1.1-1 on Artix Linux.

Note: NO_EXTRA_CFLAGS was added to work around this issue by causing all
of the flags in EXTRA_CFLAGS to be ignored.

Note2: -mretpoline was added on commit 4a99c8aa2 ("spectre support for
clang compiler", 2018-03-30) and NO_EXTRA_CFLAGS was added on commit
490918c35 ("fix make scan-build for debian 10 and arch", 2019-07-22).
See also commit 2c64d1fdd ("use AX_CHECK_COMPILE_FLAG to check for
spectre flags", 2019-06-21).

Closes #5509.

Kind of relates to #2661.

1 files changed, 0 insertions, 4 deletions

diff --git a/configure.ac b/configure.ac
index 30b031801..93de61b95 100644
--- a/configure.ac
+++ b/configure.ac
@@ -25,10 +25,6 @@ AX_CHECK_COMPILE_FLAG([-mindirect-branch=thunk], [
         HAVE_SPECTRE="yes"
         EXTRA_CFLAGS="$EXTRA_CFLAGS -mindirect-branch=thunk"
 ])
-AX_CHECK_COMPILE_FLAG([-mretpoline], [
-        HAVE_SPECTRE="yes"
-        EXTRA_CFLAGS="$EXTRA_CFLAGS -mretpoline"
-])
 AX_CHECK_COMPILE_FLAG([-fstack-clash-protection], [
         HAVE_SPECTRE="yes"
         EXTRA_CFLAGS="$EXTRA_CFLAGS -fstack-clash-protection"