Fix Android build on 32 bit

Remove the --system=linux-x86_64 which isn't neccessary on 64 bit,
as, when given no --system parameter, the standalone-toolchain.sh script
figures out the platform on itself. Naturally, the hardcoded setting broke
android building on 32 bit systems.

build/android/Makefile

@@ -311,7 +311,7 @@ $(OPENSSL_LIB): $(OPENSSL_TIMESTAMP)
 	export TOOLCHAIN=/tmp/ndk-${TARGET_HOST}-openssl;                          \
 	${ANDROID_NDK}/build/tools/make-standalone-toolchain.sh                    \
 	--toolchain=${TARGET_TOOLCHAIN}${COMPILER_VERSION}                         \
-	--install-dir=$${TOOLCHAIN} --system=linux-x86_64;                         \
+	--install-dir=$${TOOLCHAIN};                                               \
 	export PATH="$${TOOLCHAIN}/bin:$${PATH}";                                  \
 	CC=${CROSS_PREFIX}gcc ./Configure android-${TARGET_ARCH} no-idea no-seed -no-sha0 -DL_ENDIAN;\
 	CC=${CROSS_PREFIX}gcc ANDROID_DEV=/tmp/ndk-${TARGET_HOST} make build_libs; \
@@ -359,7 +359,7 @@ $(LEVELDB_LIB): $(LEVELDB_TIMESTAMP)
 	export TOOLCHAIN=/tmp/ndk-${TARGET_HOST}-leveldb;                          \
 	${ANDROID_NDK}/build/tools/make-standalone-toolchain.sh                    \
 	--toolchain=${TARGET_TOOLCHAIN}${COMPILER_VERSION}                         \
-	--install-dir=$${TOOLCHAIN} --system=linux-x86_64;                         \
+	--install-dir=$${TOOLCHAIN};                                               \
 	export PATH="$${TOOLCHAIN}/bin:$${PATH}";                                  \
 	export CC=${CROSS_PREFIX}gcc;                                              \
 	export CXX=${CROSS_PREFIX}g++;                                             \
@@ -518,7 +518,7 @@ $(CURL_LIB): $(CURL_TIMESTAMP) $(OPENSSL_LIB)
 	export TOOLCHAIN=/tmp/ndk-${TARGET_HOST}-curl;                             \
 	${ANDROID_NDK}/build/tools/make-standalone-toolchain.sh                    \
 	--toolchain=${TARGET_TOOLCHAIN}${COMPILER_VERSION}                         \
-	--install-dir=$${TOOLCHAIN} --system=linux-x86_64;                         \
+	--install-dir=$${TOOLCHAIN};                                               \
 	export PATH="$${TOOLCHAIN}/bin:$${PATH}";                                  \
 	export CC=${CROSS_PREFIX}gcc;                                              \
 	export CXX=${CROSS_PREFIX}g++;                                             \