boost: android-aarch64: disable various overrides

sysroot and gcc-toolchain seem to be unneeded with toolchain with
platform versions in triplets.
Also unified the header search paths to use those headers from llvm
toolchain as much as possible.

This seems to fix the problem with dlopen refusing to load with "using
IE access model".

boost/android-aarch64/PKGBUILD

@@ -9,7 +9,7 @@ _android_arch=arm64-v8a
 _android_toolchain=$_pkg_arch-linux-android
 _andoird_toolchain_dir=$_android_toolchain
 _android_platform=24
-_android_target=$_android_toolchain
+_android_target=$_android_toolchain$_android_platform
 _android_prefix=/opt/android-libs/$_pkg_arch
 _android_ndk_path=/opt/android-ndk
 _boost_arch=arm
@@ -18,7 +18,7 @@ _boost_address_model=64
 pkgname=android-$_pkg_arch-$_pkgname
 pkgver=1.75.0
 _boostver=${pkgver//./_}
-pkgrel=1
+pkgrel=2
 url='https://www.boost.org/'
 arch=('any')
 license=('custom')
@@ -42,14 +42,10 @@ build() {
   local _stagedir="${srcdir}/stagedir"
   local jobs="$(sed -e 's/.*\(-j *[0-9]\+\).*/\1/' <<< ${MAKEFLAGS})"
   local target_flags=" \
-    --target=$_android_target \
-    --gcc-toolchain=$_android_ndk_path/toolchains/$_andoird_toolchain_dir-4.9/prebuilt/linux-x86_64 \
-    --sysroot=$_android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr"
+    --target=$_android_target"
   local common_flags=" \
     $target_flags \
-    -isystem $_android_ndk_path/sources/android/support/include \
-    -isystem $_android_ndk_path/sources/cxx-stl/llvm-libc++/include \
-    -isystem $_android_ndk_path/sources/cxx-stl/llvm-libc++abi/include \
+    -isystem $_android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/c++/v1 \
     -isystem $_android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include \
     -isystem $_android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/include/$_android_toolchain \
     -fexceptions \
@@ -62,7 +58,6 @@ build() {
     $target_flags \
     -fexceptions \
     $_android_ndk_path/sources/cxx-stl/llvm-libc++/libs/$_android_arch/libc++_shared.so \
-    -B$_android_ndk_path/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/$_android_toolchain/$_android_platform \
     -nostdlib++"
 
   cd ${_pkgname}_${_boostver}