libcxx: Remove -flto from LDFLAGS

It seems the buildbots can't handle it.

Added a cmake option to find the cxxabi files as they are part of the
toolchain and not in the normal path. It doesn't seem to make a
difference, just gets rid of cmake warnings.

Added another small GCC warning fix. It's fairly minor.

This has no change in compiled size, and most likely no change in
behavior. Bumped the PKG_RELEASE anyway.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

package/libs/libcxx/Makefile

@@ -1,3 +1,4 @@
+
 #
 # This is free software, licensed under the GNU General Public License v2.
 # See /LICENSE for more information.
@@ -7,7 +8,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=libcxx
 PKG_VERSION:=9.0.1
-PKG_RELEASE:=3
+PKG_RELEASE:=4
 
 PKG_SOURCE_PROTO:=git
 PKG_SOURCE_URL:=https://git.llvm.org/git/libcxx
@@ -38,6 +39,7 @@ endef
 
 CMAKE_OPTIONS += \
 	-DLIBCXX_CXX_ABI="libsupc++" \
+	-DLIBCXX_CXX_ABI_INCLUDE_PATHS="$(TOOLCHAIN_DIR)/$(REAL_GNU_TARGET_NAME)/include/c++/$(CONFIG_GCC_VERSION);$(TOOLCHAIN_DIR)/$(REAL_GNU_TARGET_NAME)/include/c++/$(CONFIG_GCC_VERSION)/$(REAL_GNU_TARGET_NAME)" \
 	-DLIBCXX_ENABLE_ASSERTIONS=OFF \
 	-DLIBCXX_ENABLE_EXPERIMENTAL_LIBRARY=OFF \
 	-DLIBCXX_INCLUDE_BENCHMARKS=OFF \
@@ -47,7 +49,7 @@ CMAKE_OPTIONS += \
 	-DLIBCXX_HAS_MUSL_LIBC=$(if $(CONFIG_USE_MUSL),ON,OFF)
 
 TARGET_CXXFLAGS += -D_LIBCPP_DISABLE_DEPRECATION_WARNINGS -Wno-attributes -flto
-TARGET_LDFLAGS += -Wl,--gc-sections,--as-needed -flto=jobserver
+TARGET_LDFLAGS += -Wl,--gc-sections,--as-needed
 
 define Build/InstallDev
 	$(call Build/InstallDev/cmake,$(1))

package/libs/libcxx/patches/010-cxx17.patch

@@ -1,6 +1,6 @@
 --- a/CMakeLists.txt
 +++ b/CMakeLists.txt
-@@ -524,9 +524,9 @@ remove_flags(-Wno-pedantic -pedantic-errors -pedantic)
+@@ -524,9 +524,9 @@ remove_flags(-Wno-pedantic -pedantic-err
  if (LIBCXX_HAS_MUSL_LIBC OR LIBCXX_TARGETING_CLANG_CL)
    # musl's pthread implementations uses volatile types in their structs which is
    # not a constexpr in C++11 but is in C++14, so we use C++14 with musl.

package/libs/libcxx/patches/020-fixes.patch

@@ -1,6 +1,17 @@
+--- a/include/cmath
++++ b/include/cmath
+@@ -615,7 +615,7 @@ _Fp __lerp(_Fp __a, _Fp __b, _Fp __t) no
+ 
+     if (__t == 1) return __b;
+     const _Fp __x = __a + __t * (__b - __a);
+-    if (__t > 1 == __b > __a)
++    if ((__t > 1) == (__b > __a))
+     	return __b < __x ? __x : __b;
+     else
+     	return __x < __b ? __x : __b;
 --- a/include/memory
 +++ b/include/memory
-@@ -1696,7 +1696,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
+@@ -1696,7 +1696,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_tr
              ptrdiff_t _Np = __end1 - __begin1;
              __end2 -= _Np;
              if (_Np > 0)