Add option for generating coverage info.

To enable building with coverage, the environment variable
NATIVE_COVERAGE must be set to true.

Set `LOCAL_NATIVE_COVERAGE := true` to generate coverage information for
a given component.

This is currently not supported for clang (b/17574078, b/17583330).

If static library A is included in a binary B (dynamic or static
executable, or shared library), and A is built with coverage
information, B is required to link with libgcov.a. Since the make does
not offer a good way to track this dependency, link libgcov.a even if
LOCAL_NATIVE_COVERAGE is not set (but still guarded by NATIVE_COVERAGE).
This ensures that all of the libgcov dependencies will always be
resolved, and causes no change in the resulting binary if coverage is
not used.

Bug: 10134489
Change-Id: Id5a19f2c215e4be80e6eae27ecc19b582f2f6813
diff --git a/core/combo/TARGET_linux-arm64.mk b/core/combo/TARGET_linux-arm64.mk
index 82eb7fd..f0fab7b 100644
--- a/core/combo/TARGET_linux-arm64.mk
+++ b/core/combo/TARGET_linux-arm64.mk
@@ -131,6 +131,8 @@
 	-print-libgcc-file-name)
 TARGET_LIBATOMIC := $(shell $(TARGET_CC) $(TARGET_GLOBAL_CFLAGS) \
 	-print-file-name=libatomic.a)
+TARGET_LIBGCOV := $(shell $(TARGET_CC) $(TARGET_GLOBAL_CFLAGS) \
+	-print-file-name=libgcov.a)
 
 KERNEL_HEADERS_COMMON := $(libc_root)/kernel/uapi
 KERNEL_HEADERS_ARCH   := $(libc_root)/kernel/uapi/asm-$(TARGET_ARCH)
@@ -177,6 +179,7 @@
 	$(PRIVATE_TARGET_GLOBAL_LDFLAGS) \
 	$(PRIVATE_LDFLAGS) \
 	$(PRIVATE_TARGET_LIBATOMIC) \
+	$(if $(filter true,$(NATIVE_COVERAGE)),$(PRIVATE_TARGET_LIBGCOV)) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_SO_O)) \
 	$(PRIVATE_LDLIBS)
@@ -204,6 +207,7 @@
 	$(PRIVATE_TARGET_GLOBAL_LDFLAGS) \
 	$(PRIVATE_LDFLAGS) \
 	$(PRIVATE_TARGET_LIBATOMIC) \
+	$(if $(filter true,$(NATIVE_COVERAGE)),$(PRIVATE_TARGET_LIBGCOV)) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_O)) \
 	$(PRIVATE_LDLIBS)
@@ -227,6 +231,7 @@
 	$(call normalize-target-libraries,$(filter %libc_nomalloc.a,$(PRIVATE_ALL_STATIC_LIBRARIES))) \
 	$(PRIVATE_TARGET_FDO_LIB) \
 	$(PRIVATE_TARGET_LIBATOMIC) \
+	$(if $(filter true,$(NATIVE_COVERAGE)),$(PRIVATE_TARGET_LIBGCOV)) \
 	$(if $(PRIVATE_LIBCXX),,$(PRIVATE_TARGET_LIBGCC)) \
 	-Wl,--end-group \
 	$(if $(filter true,$(PRIVATE_NO_CRT)),,$(PRIVATE_TARGET_CRTEND_O))