Rework go bindings so that validation works fine

Basically change the layout to please `go build` and remove references to
`llvm-go`.

Update llvm/test/Bindings/Go/ to use the system go compiler

Differential Revision: https://reviews.llvm.org/D74540

Author: serge-sans-paille

llvm/bindings/go/build.sh

@@ -14,5 +14,3 @@
 // +build !byollvm
 
 package llvm
-
-var _ run_build_sh

llvm/bindings/go/llvm/IRBindings.cpp renamed to llvm/bindings/go/src/llvm/IRBindings.cpp

@@ -1,4 +1,4 @@
-; RUN: llvm-go test llvm.org/llvm/bindings/go/llvm
+; RUN: CGO_CPPFLAGS="`llvm-config --cppflags`" CGO_CXXFLAGS=-std=c++14 CGO_LDFLAGS="`llvm-config --ldflags --libs --system-libs all`" go test llvm
 
 ; REQUIRES: shell
 ; UNSUPPORTED: asan, ubsan, msan

llvm/bindings/go/llvm/IRBindings.h renamed to llvm/bindings/go/src/llvm/IRBindings.h

@@ -57,4 +57,5 @@ def fixup_compiler_path(compiler):
 
 config.environment['CC'] = fixup_compiler_path(config.host_cc)
 config.environment['CXX'] = fixup_compiler_path(config.host_cxx)
-config.environment['CGO_LDFLAGS'] = config.host_ldflags
+config.environment['LD_LIBRARY_PATH'] = config.llvm_shlib_dir
+config.environment['GOPATH'] = os.path.join(config.llvm_src_root, 'bindings', 'go')

llvm/bindings/go/llvm/InstrumentationBindings.cpp renamed to llvm/bindings/go/src/llvm/InstrumentationBindings.cpp

@@ -160,7 +160,7 @@ def get_asan_rtlib():
 
 # The following tools are optional
 tools.extend([
-    ToolSubst('llvm-go', unresolved='ignore'),
+    ToolSubst('go', unresolved='ignore'),
     ToolSubst('llvm-mt', unresolved='ignore'),
     ToolSubst('Kaleidoscope-Ch3', unresolved='ignore'),
     ToolSubst('Kaleidoscope-Ch4', unresolved='ignore'),

llvm/bindings/go/llvm/InstrumentationBindings.h renamed to llvm/bindings/go/src/llvm/InstrumentationBindings.h

@@ -23,7 +23,7 @@ def resolve(self, config, dirs):
 
         if self.name == 'llc' and os.environ.get('LLVM_ENABLE_MACHINE_VERIFIER') == '1':
             command += ' -verify-machineinstrs'
-        elif self.name == 'llvm-go':
+        elif self.name == 'go':
             exe = getattr(config.config, 'go_executable', None)
             if exe:
                 command += ' go=' + exe