Capture libeigen's header correctly

libeigen exports entire directory, but only two directories contain
actual exported headers. And some of headers have no extension. This
adds a special behaviour for external/eigen when capturing snapshot.

Exempt-From-Owner-Approval: cherry-pick from internal branch

Bug: 157106227
Test: m vendor-snapshot captures libeigen's headers
Change-Id: I82f27d4c6c4d472f47d54c545328150697b8cda3
Merged-In: I82f27d4c6c4d472f47d54c545328150697b8cda3
(cherry picked from commit 67f3dbca2f)

cc/library.go

@@ -407,6 +407,31 @@ func (l *libraryDecorator) collectHeadersForSnapshot(ctx android.ModuleContext)
 		if strings.HasPrefix(dir, android.PathForOutput(ctx).String()) {
 			continue
 		}
+		// libeigen wrongly exports the root directory "external/eigen". But only two
+		// subdirectories "Eigen" and "unsupported" contain exported header files. Even worse
+		// some of them have no extension. So we need special treatment for libeigen in order
+		// to glob correctly.
+		if dir == "external/eigen" {
+			// Only these two directories contains exported headers.
+			for _, subdir := range []string{"Eigen", "unsupported/Eigen"} {
+				glob, err := ctx.GlobWithDeps("external/eigen/"+subdir+"/**/*", nil)
+				if err != nil {
+					ctx.ModuleErrorf("glob failed: %#v", err)
+					return
+				}
+				for _, header := range glob {
+					if strings.HasSuffix(header, "/") {
+						continue
+					}
+					ext := filepath.Ext(header)
+					if ext != "" && ext != ".h" {
+						continue
+					}
+					ret = append(ret, android.PathForSource(ctx, header))
+				}
+			}
+			continue
+		}
 		exts := headerExts
 		// Glob all files under this special directory, because of C++ headers.
 		if strings.HasPrefix(dir, "external/libcxx/include") {