[i686 Linux] Bootstrap the build

Prior to this, the swift build didn’t understand what i686 is, or what to do about building it. This unblocks building, but will still run into build breaks.

Author: Kaiede

CMakeLists.txt

@@ -592,7 +592,7 @@ else()
     set(SWIFT_HOST_VARIANT_ARCH_default "x86_64")
   elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "IA64")
     set(SWIFT_HOST_VARIANT_ARCH_default "itanium")
-  elseif("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86")
+  elseif("${CMAKE_SYSTEM_PROCESSOR}" MATCHES "(x86|i686)")
     set(SWIFT_HOST_VARIANT_ARCH_default "i686")
   else()
     message(FATAL_ERROR "Unrecognized architecture on host system: ${CMAKE_SYSTEM_PROCESSOR}")
@@ -647,6 +647,8 @@ if("${SWIFT_HOST_VARIANT_SDK}" STREQUAL "LINUX")
   if("${SWIFT_HOST_TRIPLE}" STREQUAL "")
     if("${SWIFT_HOST_VARIANT_ARCH}" STREQUAL "x86_64")
       set(SWIFT_HOST_TRIPLE "x86_64-unknown-linux-gnu")
+    elseif("${SWIFT_HOST_VARIANT_ARCH}" STREQUAL "i686")
+      set(SWIFT_HOST_TRIPLE "i686-unknown-linux-gnu")
     elseif("${SWIFT_HOST_VARIANT_ARCH}" STREQUAL "aarch64")
       set(SWIFT_HOST_TRIPLE "aarch64-unknown-linux-gnu")
     elseif("${SWIFT_HOST_VARIANT_ARCH}" MATCHES "(powerpc64|powerpc64le)")

utils/build-script-impl

@@ -433,6 +433,9 @@ function set_build_options_for_host() {
                 linux-x86_64)
                     SWIFT_HOST_VARIANT_ARCH="x86_64"
                     ;;
+                linux-i686)
+                    SWIFT_HOST_VARIANT_ARCH="i686"
+                    ;;
                 linux-armv6)
                     SWIFT_HOST_VARIANT_ARCH="armv6"
                     SWIFT_HOST_TRIPLE="armv6-unknown-linux-gnueabihf"

utils/swift_build_support/swift_build_support/targets.py

@@ -113,6 +113,7 @@ class StdlibDeploymentTarget(object):
 
     Linux = Platform("linux", archs=[
         "x86_64",
+        "i686",
         "armv6",
         "armv7",
         "aarch64",
@@ -160,6 +161,8 @@ def host_target():
         if system == 'Linux':
             if machine == 'x86_64':
                 return StdlibDeploymentTarget.Linux.x86_64
+            elif machine == 'i686':
+                return StdlibDeploymentTarget.Linux.i686
             elif machine.startswith('armv7'):
                 # linux-armv7* is canonicalized to 'linux-armv7'
                 return StdlibDeploymentTarget.Linux.armv7