Backport check for Thumb instructions from configure script

The recompiler can't handle Thumb instructions, so they must be disabled.
This is accomplished via the `-marm` flag being set for different platforms.

However, when using `platform=unix` and manually configuring the build,
the check for Thumb instructions is not done in `Makefile.libretro`.
Therefore, when building with a compiler that defaults to Thumb instructions
(e.g. ODROID-XU4), the build can fail with this error:

    libpcsxcore/new_dynarec/backends/psx/pcsxmem.c:18:2: error:
     #error the dynarec is incompatible with Thumb functions,
    libpcsxcore/new_dynarec/backends/psx/pcsxmem.c:19:2: error:
     #error please add -marm to compile flags

To address this, we simply backport the define check from the configure script
for when we build with `ARCH=arm`. This change doesn't affect the buildbot.

diff --git a/Makefile.libretro b/Makefile.libretro
index 5a59aea..2cda1d0 100644 (file)
--- a/Makefile.libretro
+++ b/Makefile.libretro
@@ -47,6 +47,12 @@ ifeq ($(platform), unix)
 ifneq ($(findstring SunOS,$(shell uname -s)),)
        CC = gcc
 endif
+ifeq ($(ARCH), arm)
+ifneq ($(findstring __thumb__,$(shell $(CC) -E -dD $(CFLAGS) include/arm_features.h)),)
+       # must disable thumb as recompiler can't handle it
+       CFLAGS += -marm
+endif
+endif
 
 else ifeq ($(platform), linux-portable)
        TARGET := $(TARGET_NAME)_libretro.so