Update boost library detection logic for cross compiling

When cross compiling for aarch64 on an x86_64 host, the build system
assumes that the boost library is placed in
"build/downloaded_packages/aarch64/boost/install". This assumption
works well on systems where cross libraries are not provided and need
to be manually installed but does not support using multiarch distros
that use standard location for cross libraries that the cross compiler
can resolve.

Update the boost library detection logic to first use the compiler to
resolve the boost libraries (both during native and cross-builds) and
failing that for aarch64 falling back to looking in the hardcoded path.

Signed-off-by: Punit Agrawal <[email protected]>
Message-Id: <[email protected]>

Makefile

@@ -1847,22 +1847,20 @@ endif
 
 #Allow user specify non-default location of boost
 ifeq ($(boost_base),)
-    ifeq ($(CROSS_PREFIX),)
-        # link with -mt if present, else the base version (and hope it is multithreaded)
-        boost-mt := -mt
+    # link with -mt if present, else the base version (and hope it is multithreaded)
+    boost-mt := -mt
+    boost-lib-dir := $(dir $(shell $(CC) --print-file-name libboost_system$(boost-mt).a))
+    ifeq ($(filter /%,$(boost-lib-dir)),)
+        boost-mt :=
         boost-lib-dir := $(dir $(shell $(CC) --print-file-name libboost_system$(boost-mt).a))
-        ifeq ($(filter /%,$(boost-lib-dir)),)
-            boost-mt :=
-            boost-lib-dir := $(dir $(shell $(CC) --print-file-name libboost_system$(boost-mt).a))
-            ifeq ($(filter /%,$(boost-lib-dir)),)
-                $(error Error: libboost_system.a needs to be installed.)
-            endif
-        endif
-        # When boost_env=host, we won't use "-nostdinc", so the build machine's
-        # header files will be used normally. So we don't need to add anything
-        # special for Boost.
-        boost-includes =
-    else
+    endif
+    # When boost_env=host, we won't use "-nostdinc", so the build machine's
+    # header files will be used normally. So we don't need to add anything
+    # special for Boost.
+    boost-includes =
+    ifeq ($(filter /%,$(boost-lib-dir)),)
+        # If the compiler cannot find the boost library, for aarch64 we look in a
+        # special location before giving up.
         ifeq ($(arch),aarch64)
             aarch64_boostbase = build/downloaded_packages/aarch64/boost/install
             ifeq (,$(wildcard $(aarch64_boostbase)))
@@ -1872,6 +1870,8 @@ ifeq ($(boost_base),)
             boost-lib-dir := $(firstword $(dir $(shell find $(aarch64_boostbase)/ -name libboost_system*.a)))
             boost-mt := $(if $(filter %-mt.a, $(wildcard $(boost-lib-dir)/*.a)),-mt)
             boost-includes = -isystem $(aarch64_boostbase)/usr/include
+        else
+            $(error Error: libboost_system.a needs to be installed.)
         endif
     endif
 else

modules/common.gmk

@@ -123,16 +123,14 @@ endif
 # Let us detect presence of boost headers and library
 # Allow user specify non-default location of boost
 ifeq ($(boost_base),)
-    ifeq ($(CROSS_PREFIX),)
-        boost-lib-dir := $(dir $(shell $(CC) --print-file-name libboost_system.so))
-        ifeq ($(filter /%,$(boost-lib-dir)),)
-            $(error Error: libboost_system.so needs to be installed.)
-        endif
-        # When boost_env=host, we won't use "-nostdinc", so the build machine's
-        # header files will be used normally. So we don't need to add anything
-        # special for Boost.
-        boost-includes =
-    else
+    boost-lib-dir := $(dir $(shell $(CC) --print-file-name libboost_system.so))
+    # When boost_env=host, we won't use "-nostdinc", so the build machine's
+    # header files will be used normally. So we don't need to add anything
+    # special for Boost.
+    boost-includes =
+    ifeq ($(filter /%,$(boost-lib-dir)),)
+        # If the compiler cannot find the boost library, for aarch64 we look in a
+        # special location before giving up.
         ifeq ($(arch),aarch64)
             aarch64_boostbase = $(src)/build/downloaded_packages/aarch64/boost/install
             ifeq (,$(wildcard $(aarch64_boostbase)))
@@ -142,6 +140,8 @@ ifeq ($(boost_base),)
             boost-lib-dir := $(firstword $(dir $(shell find $(aarch64_boostbase)/ -name libboost_system.so)))
             LDFLAGS += -L$(boost-lib-dir)
             boost-includes = -isystem $(aarch64_boostbase)/usr/include
+        else
+            $(error Error: libboost_system.so needs to be installed.)
         endif
     endif
 else