[gnome-continuous-yocto/gnomeostree-3.28-rocko: 8047/8267] musl: use a more specific fix for ARM thumb + frame pointers

[Emmanuele Bassi <ebassi src gnome org>]

commit 65458b6e83eec3d44cc7ad7f67ee792d94bdeaa8
Author: Andre McCurdy <armccurdy gmail com>
Date:   Mon Oct 9 09:00:35 2017 -0700

    musl: use a more specific fix for ARM thumb + frame pointers
    
    When compiling for Thumb or Thumb2, frame pointers _must_ be disabled
    since the Thumb frame pointer in r7 clashes with musl's use of inline
    asm to make syscalls (where r7 is used for the syscall NR).
    
    In most cases, frame pointers will be disabled automatically due to
    the optimisation level, but appending an explicit -fomit-frame-pointer
    to CFLAGS handles cases where optimisation is set to -O0 or frame
    pointers have been enabled by -fno-omit-frame-pointer earlier in
    CFLAGS, etc.
    
    Note that this limitation applies both to gcc and clang, the only
    difference between the two being that where gcc aborts with an error
    about reusing r7, clang apparently silently generates broken code:
    
      https://bugs.llvm.org/show_bug.cgi?id=34165
    
    (From OE-Core rev: d7580cd7792982fd9e98086e4edc490635e9adca)
    
    Signed-off-by: Andre McCurdy <armccurdy gmail com>
    Signed-off-by: Ross Burton <ross burton intel com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>

 meta/recipes-core/musl/musl_git.bb |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)
---
diff --git a/meta/recipes-core/musl/musl_git.bb b/meta/recipes-core/musl/musl_git.bb
index 8b6a2e3..bd7573e 100644
--- a/meta/recipes-core/musl/musl_git.bb
+++ b/meta/recipes-core/musl/musl_git.bb
@@ -28,7 +28,13 @@ export CROSS_COMPILE="${TARGET_PREFIX}"
 
 LDFLAGS += "-Wl,-soname,libc.so"
 
-ARM_INSTRUCTION_SET_toolchain-clang = "arm"
+# When compiling for Thumb or Thumb2, frame pointers _must_ be disabled since the
+# Thumb frame pointer in r7 clashes with musl's use of inline asm to make syscalls
+# (where r7 is used for the syscall NR). In most cases, frame pointers will be
+# disabled automatically due to the optimisation level, but append an explicit
+# -fomit-frame-pointer to handle cases where optimisation is set to -O0 or frame
+# pointers have been enabled by -fno-omit-frame-pointer earlier in CFLAGS, etc.
+CFLAGS_append_arm = " ${@bb.utils.contains('TUNE_CCARGS', '-mthumb', '-fomit-frame-pointer', '', d)}"
 
 CONFIGUREOPTS = " \
     --prefix=${prefix} \