Add a custom script to build premake, like NVTT, FCollada, and Spidermonkey.

Fix an issue on newer GNU/Linux and macOS where the build would fail due
to missing unistd includes.
Fixes: #6847
Accepted by: @vv221
Comments by: @sera
Differential Revision: https://code.wildfiregames.com/D4894
This was SVN commit r28187.

build/premake/build.sh

@@ -0,0 +1,35 @@
+#!/bin/sh
+set -e
+
+LIB_VERSION="premake-5-alpha-14+wildfiregames.1"
+
+if [ -e .already-built ] && [ "$(cat .already-built)" = "${LIB_VERSION}" ]
+then
+  echo "Premake 5 is already up to date."
+  exit
+fi
+
+JOBS=${JOBS:="-j2"}
+MAKE=${MAKE:="make"}
+CFLAGS="${CFLAGS:=""} -Wno-error=implicit-function-declaration"
+OS="${OS:=$(uname -s)}"
+
+echo "Building Premake 5..."
+echo
+
+PREMAKE_BUILD_DIR=premake5/build/gmake2.unix
+# BSD and OS X need different Makefiles
+case "$OS" in
+"GNU/kFreeBSD" )
+    # use default gmake2.unix (needs -ldl as we have a GNU userland and libc)
+    ;;
+*"BSD" )
+    PREMAKE_BUILD_DIR=premake5/build/gmake2.bsd
+    ;;
+"Darwin" )
+    PREMAKE_BUILD_DIR=premake5/build/gmake2.macosx
+    ;;
+esac
+${MAKE} -C "${PREMAKE_BUILD_DIR}" "${JOBS}" CFLAGS="$CFLAGS" config=release
+
+echo "${LIB_VERSION}" > .already-built

build/workspaces/update-workspaces.sh

@@ -102,30 +102,15 @@ if [ "`uname -s`" != "Darwin" ]; then
   echo
 fi
 
-# Now run premake to create the makefiles
+# Now build Premake or use system's.
 
 cd ../premake
 premake_command="premake5"
 
 if [ "$with_system_premake5" = "false" ]; then
   # Build bundled premake
-  cd premake5
+  MAKE=${MAKE} JOBS=${JOBS} ./build.sh || die "Premake 5 build failed"
-  PREMAKE_BUILD_DIR=build/gmake2.unix
-  # BSD and OS X need different Makefiles
-  case "`uname -s`" in
-    "GNU/kFreeBSD" )
-      # use default gmake2.unix (needs -ldl as we have a GNU userland and libc)
-      ;;
-    *"BSD" )
-      PREMAKE_BUILD_DIR=build/gmake2.bsd
-      ;;
-    "Darwin" )
-      PREMAKE_BUILD_DIR=build/gmake2.macosx
-      ;;
-  esac
-  ${MAKE} -C $PREMAKE_BUILD_DIR ${JOBS} || die "Premake build failed"
 
-  cd ..
   premake_command="premake5/bin/release/premake5"
 fi
 
@@ -133,7 +118,7 @@ echo
 
 # If we're in bash then make HOSTTYPE available to Premake, for primitive arch-detection
 export HOSTTYPE="$HOSTTYPE"
-
+# Now run Premake to create the makefiles
 echo "Premake args: ${premake_args}"
 if [ "`uname -s`" != "Darwin" ]; then
   ${premake_command} --file="premake5.lua" --outpath="../workspaces/gcc/" ${premake_args} gmake || die "Premake failed"