adb: Don't force -O2

Don't force -O2 over -O3 -- the O2 hardcode is there to force
optimizations, not to reduce them...

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
corkscrew-x86: Fix build with some glibc versions

Make sure __USE_GNU is actually set before ucontext.h is included
(even implicitly).
This should fix the build inside android-build (wasn't broken locally
in the first place).

Signed-off-by: Amit Pundir <amit.pundir@linaro.org>

Conflicts:
	libcorkscrew/arch-x86/backtrace-x86.c
adb: Link to libdl manually to avoid build failure on android-build

An outdated build environment results in a host adb build failure
because libcrypto needs libdl, but libdl isn't linked explicitly:
out/host/linux-x86/obj/STATIC_LIBRARIES/libcrypto_static_intermediates/libcrypto_static.a(dso_dlfcn.o):
In function `dlfcn_globallookup':
/mnt/jenkins/workspace/linaro-android_galaxynexus-jb-gcc47-aosp-blob/build/external/openssl/crypto/dso/dso_dlfcn.c:474:
undefined reference to `dlopen'
/mnt/jenkins/workspace/linaro-android_galaxynexus-jb-gcc47-aosp-blob/build/external/openssl/crypto/dso/dso_dlfcn.c:478:
undefined reference to `dlsym'
/mnt/jenkins/workspace/linaro-android_galaxynexus-jb-gcc47-aosp-blob/build/external/openssl/crypto/dso/dso_dlfcn.c:479:
undefined reference to `dlclose'
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
More libcorkscrew fixes for GCC 4.8+