Android - Support cross-compiling System.Native for Android (dotnet/c…

…orefx#15912)

* Last batch of fixes to get compilation to run on Android
* Move the MNTOPT_RO definition inside HAVE_MNTINFO to avoid a unused identifier


Commit migrated from dotnet/corefx@b5b0a77

src/libraries/Native/Unix/System.Native/CMakeLists.txt

@@ -42,7 +42,7 @@ add_library(System.Native-Static
 SET_TARGET_PROPERTIES(System.Native-Static PROPERTIES PREFIX "")
 SET_TARGET_PROPERTIES(System.Native-Static PROPERTIES OUTPUT_NAME System.Native CLEAN_DIRECT_OUTPUT 1)
 
-if (CMAKE_SYSTEM_NAME STREQUAL Linux)
+if (CMAKE_SYSTEM_NAME STREQUAL Linux AND NOT CLR_CMAKE_PLATFORM_ANDROID)
     target_link_libraries(System.Native rt)
 endif ()
 

src/libraries/Native/Unix/System.Native/pal_mount.cpp

@@ -16,6 +16,11 @@
 #include <sys/statfs.h>
 #include <mntent.h>
 #define STRING_BUFFER_SIZE 8192
+
+// Android does not define MNTOPT_RO
+#ifndef MNTOPT_RO
+#define MNTOPT_RO "r"
+#endif
 #endif
 
 static int32_t GetMountInfo(MountPointFound onFound)

src/libraries/Native/Unix/configure.cmake

@@ -294,6 +294,10 @@ set(HAVE_THREAD_SAFE_GETHOSTBYNAME_AND_GETHOSTBYADDR 0)
 if (CMAKE_SYSTEM_NAME STREQUAL Linux)
     set(CMAKE_REQUIRED_LIBRARIES rt)
     set(HAVE_SUPPORT_FOR_DUAL_MODE_IPV4_PACKET_INFO 1)
+
+    if (CLR_CMAKE_PLATFORM_ANDROID)
+       set(HAVE_THREAD_SAFE_GETHOSTBYNAME_AND_GETHOSTBYADDR 1)
+    endif()
 elseif (CMAKE_SYSTEM_NAME STREQUAL Darwin)
     set(HAVE_THREAD_SAFE_GETHOSTBYNAME_AND_GETHOSTBYADDR 1)
 endif ()
@@ -463,8 +467,11 @@ check_cxx_source_compiles(
     HAVE_TCP_VAR_H
 )
 
+# If sys/cdefs is not included on Android, this check will fail because
+# __BEGIN_DECLS is not defined
 check_cxx_source_compiles(
     "
+    #include <sys/cdefs.h>
     #include <netinet/tcp.h>
     int main() { int x = TCP_ESTABLISHED; return x; }
     "