Add Go support to default_target_compile

This adds Go support to default_target_compile.  This comes from this
gdb patch:

    commit a766d390bb857383a5f9ae80a102e1f8705f4c2e
    Author: Doug Evans <dje@google.com>
    Date:   Wed Apr 25 14:07:23 2012 +0000

		Initial pass at Go language support.

2 files changed, 55 insertions, 0 deletions

diff --git a/lib/libgloss.exp b/lib/libgloss.exp
index 522e864..8e8a9ce 100644
--- a/lib/libgloss.exp
+++ b/lib/libgloss.exp
@@ -765,6 +765,30 @@ proc find_gnatmake {} {
     return $CC
 }
 
+proc find_go {} {
+    global tool_root_dir
+
+    set GO ""
+
+    if {![is_remote host]} {
+	set file [lookfor_file $tool_root_dir gccgo]
+	if { $file ne "" } {
+	    set root [file dirname $file]
+	    set GO "$file -B$root/gcc/"
+	}
+    }
+
+    if { $GO eq "" } {
+	set GO [transform gccgo]
+    }
+
+    return $GO
+}
+
+proc find_go_linker {} {
+    return [find_go]
+}
+
 proc find_rustc {} {
     global tool_root_dir
     if {![is_remote host]} {
diff --git a/lib/target.exp b/lib/target.exp
index 132c1a3..57f3b3a 100644
--- a/lib/target.exp
+++ b/lib/target.exp
@@ -400,6 +400,26 @@ proc default_target_compile {source destfile type options} {
 	    }
 	}
 
+	if { $i eq "go" } {
+	    set compiler_type "go"
+	    if {[board_info $dest exists goflags]} {
+		append add_flags " [board_info $dest goflags]"
+	    }
+	    if {[board_info $dest exists gocompiler]} {
+		set compiler [board_info $dest gocompiler]
+	    } else {
+		set compiler [find_go]
+	    }
+	    if {[board_info $dest exists golinker]} {
+		set linker [board_info $dest golinker]
+	    } else {
+		set linker [find_go_linker]
+	    }
+	    if {[board_info $dest exists golinker_opts_order]} {
+		set linker_opts_order [board_info $dest golinker_opts_order]
+	    }
+	}
+
 	if { $i eq "rust" } {
 	    set compiler_type "rust"
 	    if {[board_info $dest exists rustflags]} {
@@ -472,6 +492,8 @@ proc default_target_compile {source destfile type options} {
     global F77_FOR_TARGET
     global F90_FOR_TARGET
     global GNATMAKE_FOR_TARGET
+    global GO_FOR_TARGET
+    global GO_LD_FOR_TARGET
     global RUSTC_FOR_TARGET
 
     if {[info exists GNATMAKE_FOR_TARGET]} {
@@ -510,6 +532,15 @@ proc default_target_compile {source destfile type options} {
 	}
     }
 
+    if { $compiler_type eq "go" } {
+	if {[info exists GO_FOR_TARGET]} {
+	    set compiler $GO_FOR_TARGET
+	}
+	if {[info exists GO_LD_FOR_TARGET]} {
+	    set linker $GO_LD_FOR_TARGET
+	}
+    }
+
     if {[info exists RUSTC_FOR_TARGET]} {
 	if {$compiler_type eq "rust"} {
 	    set compiler $RUSTC_FOR_TARGET