Backport fixes for LLVM 6 support

Backport a patch to use Dwarf debuginfo v3 and build with
-DLDC_WITH_LLD=OFF, as suggested by upstream in
https://github.com/ldc-developers/ldc/pull/2608

0001-LLVM-6-Default-to-Dwarf-debuginfos-v3.patch

@@ -0,0 +1,30 @@
+From 18cf4196f66c9e11ff744d85d2803af8d593dbe3 Mon Sep 17 00:00:00 2001
+From: Martin <noone@nowhere.com>
+Date: Sun, 25 Mar 2018 17:37:34 +0200
+Subject: [PATCH] LLVM 6+: Default to Dwarf debuginfos v3
+
+At least on Linux it appears to default to v4 or newer, which druntime's
+rt.backtrace.dwarf doesn't handle yet.
+
+This fixes tests/codegen/exception_stack_trace.d on Linux.
+---
+ driver/targetmachine.cpp | 6 ++++++
+ 1 file changed, 6 insertions(+)
+
+diff --git a/driver/targetmachine.cpp b/driver/targetmachine.cpp
+index d75a31b2c..70a09127c 100644
+--- a/driver/targetmachine.cpp
++++ b/driver/targetmachine.cpp
+@@ -458,6 +458,12 @@ createTargetMachine(const std::string targetTriple, const std::string arch,
+   if (targetOptions.MCOptions.ABIName.empty())
+     targetOptions.MCOptions.ABIName = getABI(triple);
+ 
++#if LDC_LLVM_VER >= 600
++  // druntime isn't ready for Dwarf v4+ debuginfos (e.g., in rt.backtrace.dwarf).
++  if (targetOptions.MCOptions.DwarfVersion == 0)
++    targetOptions.MCOptions.DwarfVersion = 3;
++#endif
++
+   auto ldcFloatABI = floatABI;
+   if (ldcFloatABI == FloatABI::Default) {
+     switch (triple.getArch()) {

ldc.spec

@@ -30,6 +30,9 @@ Source1:        https://github.com/ldc-developers/ldc/releases/download/v%{boots
 %endif
 Source3:        macros.%{name}
 
+# https://github.com/ldc-developers/ldc/pull/2608
+Patch0:         0001-LLVM-6-Default-to-Dwarf-debuginfos-v3.patch
+
 ExclusiveArch:  %{ldc_arches}
 
 %if ! 0%{?bootstrap}
@@ -166,7 +169,7 @@ Enable autocompletion for phobos library in geany (IDE)
 Active l'autocompletion pour pour la bibliothèque phobos dans geany (IDE)
 
 %prep
-%setup -q -n %{name}-%{version}%{?pre:-%{pre}}-src
+%autosetup -n %{name}-%{version}%{?pre:-%{pre}}-src -p1
 # temp geany config directory for allow geany to generate tags
 mkdir geany_config
 
@@ -190,6 +193,7 @@ pushd build
               -DSYSCONF_INSTALL_DIR:PATH=%{_sysconfdir}             \
               -DCMAKE_INSTALL_PREFIX:PATH=%{_prefix}                \
               -DLLVM_CONFIG:PATH=%{_bindir}/llvm-config-%{__isa_bits} \
+              -DLDC_WITH_LLD:BOOL=OFF                               \
 %if 0%{?bootstrap}
               -DD_COMPILER:PATH=`pwd`/../build-bootstrap/bin/ldmd2  \
 %endif