llvmPackages_8.clang: bare-metal driver linker fix

Clang passes an incorrect -l linker flag for compiler-rt.

See https://reviews.llvm.org/D51899

pkgs/development/compilers/llvm/8/clang/compiler-rt-baremetal.patch

@@ -0,0 +1,53 @@
+Index: lib/Driver/ToolChains/BareMetal.cpp
+===================================================================
+--- a/lib/Driver/ToolChains/BareMetal.cpp
++++ b/lib/Driver/ToolChains/BareMetal.cpp
+@@ -157,7 +157,7 @@
+ void BareMetal::AddLinkRuntimeLib(const ArgList &Args,
+                                   ArgStringList &CmdArgs) const {
+   CmdArgs.push_back(Args.MakeArgString("-lclang_rt.builtins-" +
+-                                       getTriple().getArchName() + ".a"));
++                                       getTriple().getArchName()));
+ }
+ 
+ void baremetal::Linker::ConstructJob(Compilation &C, const JobAction &JA,
+Index: test/Driver/baremetal.cpp
+===================================================================
+--- a/test/Driver/baremetal.cpp
++++ b/test/Driver/baremetal.cpp
+@@ -13,7 +13,7 @@
+ // CHECK-V6M-C-NEXT: "{{[^"]*}}ld{{(\.(lld|bfd|gold))?}}{{(\.exe)?}}" "{{.*}}.o" "-Bstatic"
+ // CHECK-V6M-C-SAME: "-L[[RESOURCE_DIR:[^"]+]]{{[/\\]+}}lib{{[/\\]+}}baremetal"
+ // CHECK-V6M-C-SAME: "-T" "semihosted.lds" "-Lsome{{[/\\]+}}directory{{[/\\]+}}user{{[/\\]+}}asked{{[/\\]+}}for"
+-// CHECK-V6M-C-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m.a"
++// CHECK-V6M-C-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m"
+ // CHECK-V6M-C-SAME: "-o" "{{.*}}.o"
+ 
+ // RUN: %clang -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+@@ -35,7 +35,7 @@
+ // CHECK-V6M-DEFAULTCXX: "{{[^"]*}}ld{{(\.(lld|bfd|gold))?}}{{(\.exe)?}}" "{{.*}}.o" "-Bstatic"
+ // CHECK-V6M-DEFAULTCXX-SAME: "-L{{[^"]*}}{{[/\\]+}}lib{{(64)?}}{{[/\\]+}}clang{{[/\\]+}}{{.*}}{{[/\\]+}}lib{{[/\\]+}}baremetal"
+ // CHECK-V6M-DEFAULTCXX-SAME: "-lc++" "-lc++abi" "-lunwind"
+-// CHECK-V6M-DEFAULTCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m.a"
++// CHECK-V6M-DEFAULTCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m"
+ // CHECK-V6M-DEFAULTCXX-SAME: "-o" "{{.*}}.o"
+ 
+ // RUN: %clangxx -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+@@ -48,7 +48,7 @@
+ // CHECK-V6M-LIBCXX: "{{[^"]*}}ld{{(\.(lld|bfd|gold))?}}{{(\.exe)?}}" "{{.*}}.o" "-Bstatic"
+ // CHECK-V6M-LIBCXX-SAME: "-L{{[^"]*}}{{[/\\]+}}lib{{(64)?}}{{[/\\]+}}clang{{[/\\]+}}{{.*}}{{[/\\]+}}lib{{[/\\]+}}baremetal"
+ // CHECK-V6M-LIBCXX-SAME: "-lc++" "-lc++abi" "-lunwind"
+-// CHECK-V6M-LIBCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m.a"
++// CHECK-V6M-LIBCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m"
+ // CHECK-V6M-LIBCXX-SAME: "-o" "{{.*}}.o"
+ 
+ // RUN: %clangxx -no-canonical-prefixes %s -### -o %t.o 2>&1 \
+@@ -61,7 +61,7 @@
+ // CHECK-V6M-LIBSTDCXX: "{{[^"]*}}ld{{(\.(lld|bfd|gold))?}}{{(\.exe)?}}" "{{.*}}.o" "-Bstatic"
+ // CHECK-V6M-LIBSTDCXX-SAME: "-L{{[^"]*}}{{[/\\]+}}lib{{(64)?}}{{[/\\]+}}clang{{[/\\]+}}{{.*}}{{[/\\]+}}lib{{[/\\]+}}baremetal"
+ // CHECK-V6M-LIBSTDCXX-SAME: "-lstdc++" "-lsupc++" "-lunwind"
+-// CHECK-V6M-LIBSTDCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m.a"
++// CHECK-V6M-LIBSTDCXX-SAME: "-lc" "-lm" "-lclang_rt.builtins-armv6m"
+ // CHECK-V6M-LIBSTDCXX-SAME: "-o" "{{.*}}.o"
+ 
+ // RUN: %clangxx -no-canonical-prefixes %s -### -o %t.o 2>&1 \

pkgs/development/compilers/llvm/8/clang/default.nix

@@ -47,6 +47,8 @@ let
       # Backport for the `--unwindlib=[libgcc|compiler-rt]` flag, which is
       # needed for our bootstrapping to not interfere with C.
       ./unwindlib.patch
+      # https://reviews.llvm.org/D51899
+      ./compiler-rt-baremetal.patch
     ];
 
     postPatch = ''