Update Trusty platform docs

Author: randomPoison

src/doc/rustc/src/platform-support.md

@@ -265,7 +265,7 @@ target | std | host | notes
 [`aarch64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | ARM64 OpenBSD
 [`aarch64-unknown-redox`](platform-support/redox.md) | ✓ |  | ARM64 Redox OS
 [`aarch64-unknown-teeos`](platform-support/aarch64-unknown-teeos.md) | ? |  | ARM64 TEEOS |
-[`aarch64-unknown-trusty`](platform-support/trusty.md) | ? |  |
+[`aarch64-unknown-trusty`](platform-support/trusty.md) | ✓ |  |
 [`aarch64-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  |
 [`aarch64-wrs-vxworks`](platform-support/vxworks.md) | ✓ |  | ARM64 VxWorks OS
 `aarch64_be-unknown-linux-gnu` | ✓ | ✓ | ARM64 Linux (big-endian)
@@ -290,7 +290,7 @@ target | std | host | notes
 [`armv7-unknown-linux-uclibceabi`](platform-support/armv7-unknown-linux-uclibceabi.md) | ✓ | ✓ | Armv7-A Linux with uClibc, softfloat
 [`armv7-unknown-linux-uclibceabihf`](platform-support/armv7-unknown-linux-uclibceabihf.md) | ✓ | ? | Armv7-A Linux with uClibc, hardfloat
 [`armv7-unknown-netbsd-eabihf`](platform-support/netbsd.md) | ✓ | ✓ | Armv7-A NetBSD w/hard-float
-[`armv7-unknown-trusty`](platform-support/trusty.md) | ? |  |
+[`armv7-unknown-trusty`](platform-support/trusty.md) | ✓ |  |
 [`armv7-wrs-vxworks-eabihf`](platform-support/vxworks.md) | ✓ |  | Armv7-A for VxWorks
 [`armv7a-kmc-solid_asp3-eabi`](platform-support/kmc-solid.md) | ✓ |  | ARM SOLID with TOPPERS/ASP3
 [`armv7a-kmc-solid_asp3-eabihf`](platform-support/kmc-solid.md) | ✓ |  | ARM SOLID with TOPPERS/ASP3, hardfloat
@@ -418,7 +418,7 @@ target | std | host | notes
 `x86_64-unknown-l4re-uclibc` | ? |  |
 [`x86_64-unknown-linux-none`](platform-support/x86_64-unknown-linux-none.md) | * |  | 64-bit Linux with no libc
 [`x86_64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | 64-bit OpenBSD
-[`x86_64-unknown-trusty`](platform-support/trusty.md) | ? |  |
+[`x86_64-unknown-trusty`](platform-support/trusty.md) | ✓ |  |
 `x86_64-uwp-windows-gnu` | ✓ |  |
 [`x86_64-uwp-windows-msvc`](platform-support/uwp-windows-msvc.md) | ✓ |  |
 [`x86_64-win7-windows-gnu`](platform-support/win7-windows-gnu.md) | ✓ |   | 64-bit Windows 7 support

src/doc/rustc/src/platform-support/trusty.md

@@ -16,8 +16,10 @@ Environment (TEE) for Android.
 
 These targets are cross-compiled. They have no special requirements for the host.
 
-Support for the standard library is work-in-progress. It is expected that
-they will support alloc with the default allocator, and partially support std.
+Trusty targets have partial support for the standard library: `alloc` is fully
+supported and `std` has limited support that excludes things like filesystem
+access, network I/O, and spawning processes/threads. File descriptors are
+supported for the purpose of IPC.
 
 Trusty uses the ELF file format.