fix crosscompiling from macs to ios

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "ng-rocksdb"
 description = "Rust wrapper for Facebook's RocksDB embeddable database, fork for Nextgraph.org"
-version = "0.21.0-ngpreview.7"
+version = "0.21.0-ngpreview.87"
 edition = "2018"
 rust-version = "1.60"
 authors = ["Tyler Neely <t@jujit.su>", "David Greenberg <dsg123456789@gmail.com>", "Niko PLP <niko@nextgraph.org>"]

librocksdb-sys/rocksdb/CMakeLists.txt

@@ -44,6 +44,29 @@ project(rocksdb
   HOMEPAGE_URL https://rocksdb.org/
   LANGUAGES CXX C ASM)
 
+if(APPLE)
+  # On macOS Cmake, when cross-compiling, sometimes CMAKE_SYSTEM_PROCESSOR wrongfully stays
+  # the same as CMAKE_HOST_SYSTEM_PROCESSOR regardless the target CPU.
+  # The manual call to  set(CMAKE_SYSTEM_PROCESSOR) has to be set after the project() call.
+  # because project() might reset CMAKE_SYSTEM_PROCESSOR back to the value of CMAKE_HOST_SYSTEM_PROCESSOR.
+  # Check if CMAKE_SYSTEM_PROCESSOR is not equal to CMAKE_OSX_ARCHITECTURES
+  if(NOT CMAKE_OSX_ARCHITECTURES STREQUAL "")
+    if(NOT CMAKE_SYSTEM_PROCESSOR STREQUAL CMAKE_OSX_ARCHITECTURES)
+      # Split CMAKE_OSX_ARCHITECTURES into a list
+      string(REPLACE ";" " " ARCH_LIST ${CMAKE_OSX_ARCHITECTURES})
+      separate_arguments(ARCH_LIST UNIX_COMMAND ${ARCH_LIST})
+      # Count the number of architectures
+      list(LENGTH ARCH_LIST ARCH_COUNT)
+      # Ensure that exactly one architecture is specified
+      if(NOT ARCH_COUNT EQUAL 1)
+          message(FATAL_ERROR "CMAKE_OSX_ARCHITECTURES must have exactly one value. Current value: ${CMAKE_OSX_ARCHITECTURES}")
+      endif()
+      set(CMAKE_SYSTEM_PROCESSOR ${CMAKE_OSX_ARCHITECTURES})
+      message(STATUS "CMAKE_SYSTEM_PROCESSOR is manually set to ${CMAKE_SYSTEM_PROCESSOR}")
+    endif()
+  endif()
+endif()
+
 if(POLICY CMP0042)
   cmake_policy(SET CMP0042 NEW)
 endif()