libgo patch committed: Fix go tool to put external tests first

[Ian Lance Taylor]

When a complex package has both external and internal tests, we need
to link against the external tests first.  This patch from Dave Cheney
fixes this.  Bootstrapped on x86_64-unknown-linux-gnu.  Committed to
mainline.

Ian

diff -r c601118c5169 libgo/go/cmd/go/build.go
--- a/libgo/go/cmd/go/build.go  Tue Mar 31 10:25:51 2015 -0700
+++ b/libgo/go/cmd/go/build.go  Tue Mar 31 10:53:19 2015 -0700
@@ -1921,6 +1921,7 @@
        // and all LDFLAGS from cgo dependencies.
        apackagesSeen := make(map[*Package]bool)
        afiles := []string{}
+       xfiles := []string{}
        ldflags := b.gccArchArgs()
        cgoldflags := []string{}
        usesCgo := false
@@ -1936,7 +1937,12 @@
                if !a.p.Standard {
                        if a.p != nil && !apackagesSeen[a.p] {
                                apackagesSeen[a.p] = true
-                               if a.p.fake {
+                               if a.p.fake && a.p.external {
+                                       // external _tests, if present must 
come before
+                                       // internal _tests. Store these on a 
seperate list
+                                       // and place them at the head after 
this loop.
+                                       xfiles = append(xfiles, a.target)
+                               } else if a.p.fake {
                                        // move _test files to the top of the 
link order
                                        afiles = append([]string{a.target}, 
afiles...)
                                } else {
@@ -1945,6 +1951,7 @@
                        }
                }
        }
+       afiles = append(xfiles, afiles...)
 
        for _, a := range allactions {
                if a.p != nil {
diff -r c601118c5169 libgo/go/cmd/go/pkg.go
--- a/libgo/go/cmd/go/pkg.go    Tue Mar 31 10:25:51 2015 -0700
+++ b/libgo/go/cmd/go/pkg.go    Tue Mar 31 10:53:19 2015 -0700
@@ -83,6 +83,7 @@
        allgofiles   []string             // gofiles + IgnoredGoFiles, absolute 
paths
        target       string               // installed file for this package 
(may be executable)
        fake         bool                 // synthesized package
+       external     bool                 // synthesized external test package
        forceBuild   bool                 // this package must be rebuilt
        forceLibrary bool                 // this package is a library (even if 
named "main")
        cmdline      bool                 // defined by files listed on command 
line
diff -r c601118c5169 libgo/go/cmd/go/test.go
--- a/libgo/go/cmd/go/test.go   Tue Mar 31 10:25:51 2015 -0700
+++ b/libgo/go/cmd/go/test.go   Tue Mar 31 10:53:19 2015 -0700
@@ -692,10 +692,11 @@
                        build: &build.Package{
                                ImportPos: p.build.XTestImportPos,
                        },
-                       imports: ximports,
-                       pkgdir:  testDir,
-                       fake:    true,
-                       Stale:   true,
+                       imports:  ximports,
+                       pkgdir:   testDir,
+                       fake:     true,
+                       external: true,
+                       Stale:    true,
                }
                if pxtestNeedsPtest {
                        pxtest.imports = append(pxtest.imports, ptest)