bp2build: build static version of libstdc++.

This CL adds the ability to filter cc_library modules to only generate
their static variant of their shared variant isn't ready.

For example, the libstdc++ library is buildable as a static library,
which libc depends on. However, the shared variant of libstdc++ depends
on libc, which has to come later.

This CL introduces that abstraction to break up bp2build conversion into
more atomic steps to help with conversion.

Test: TH (bazel build //bionic/... incl. libstdc++'s static variant)
Bug: 186489250
Bug: 186822597

Change-Id: I3e2fe748e4e3d3b656760da4807f342d67c8f45f
diff --git a/android/bazel.go b/android/bazel.go
index 22d558f..9de016e 100644
--- a/android/bazel.go
+++ b/android/bazel.go
@@ -210,7 +210,6 @@
 		"libc_tzcode",           // http://b/186822591, cc_library_static, localtime.c:84:46: error: expected expression
 		"libc_bionic_ndk",       // http://b/186822256, cc_library_static, signal.cpp:186:52: error: ISO C++ requires field designators to be specified in declaration order
 		"libc_malloc_hooks",     // http://b/187016307, cc_library, ld.lld: error: undefined symbol: __malloc_hook
-		"libstdc++",             // http://b/186822597, cc_library, ld.lld: error: undefined symbol: __errno
 		"libm",                  // http://b/183064661, cc_library, math.h:25:16: error: unexpected token in argument list
 
 		// http://b/186823769: Needs C++ STL support, includes from unconverted standard libraries in //external/libcxx
@@ -237,6 +236,12 @@
 		"libjemalloc5_unittest",
 	}
 
+	// Per-module denylist of cc_library modules to only generate the static
+	// variant if their shared variant isn't ready or buildable by Bazel.
+	bp2buildCcLibraryStaticOnlyList = []string{
+		"libstdc++", // http://b/186822597, cc_library, ld.lld: error: undefined symbol: __errno
+	}
+
 	// Per-module denylist to opt modules out of mixed builds. Such modules will
 	// still be generated via bp2build.
 	mixedBuildsDisabledList = []string{
@@ -250,6 +255,7 @@
 	// Used for quicker lookups
 	bp2buildDoNotWriteBuildFile = map[string]bool{}
 	bp2buildModuleDoNotConvert  = map[string]bool{}
+	bp2buildCcLibraryStaticOnly = map[string]bool{}
 	mixedBuildsDisabled         = map[string]bool{}
 )
 
@@ -262,11 +268,19 @@
 		bp2buildModuleDoNotConvert[moduleName] = true
 	}
 
+	for _, moduleName := range bp2buildCcLibraryStaticOnlyList {
+		bp2buildCcLibraryStaticOnly[moduleName] = true
+	}
+
 	for _, moduleName := range mixedBuildsDisabledList {
 		mixedBuildsDisabled[moduleName] = true
 	}
 }
 
+func GenerateCcLibraryStaticOnly(ctx BazelConversionPathContext) bool {
+	return bp2buildCcLibraryStaticOnly[ctx.Module().Name()]
+}
+
 func ShouldWriteBuildFileForDir(dir string) bool {
 	if _, ok := bp2buildDoNotWriteBuildFile[dir]; ok {
 		return false
@@ -284,6 +298,12 @@
 	if len(b.GetBazelLabel(ctx, ctx.Module())) == 0 {
 		return false
 	}
+	if GenerateCcLibraryStaticOnly(ctx) {
+		// Don't use partially-converted cc_library targets in mixed builds,
+		// since mixed builds would generally rely on both static and shared
+		// variants of a cc_library.
+		return false
+	}
 	return !mixedBuildsDisabled[ctx.Module().Name()]
 }