[clang] [Clang] [Driver] add a Cygwin ToolChain (PR #135691)

[via cfe-commits]

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+// RUN: %clang -### %s --target=i686-pc-windows-cygnus --sysroot=%S/Inputs/basic_cygwin_tree \
+// RUN:   -resource-dir=%S/Inputs/resource_dir \
+// RUN:   --stdlib=platform 2>&1 | FileCheck --check-prefix=CHECK %s
+// CHECK:      "-cc1"
+// CHECK-SAME: "-resource-dir" "[[RESOURCE:[^"]+]]"
+// CHECK-SAME: "-isysroot" "[[SYSROOT:[^"]+]]"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[SYSROOT]]/usr/lib/gcc/i686-pc-cygwin/10/../../../../include/c++/10"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[SYSROOT]]/usr/lib/gcc/i686-pc-cygwin/10/../../../../include/i686-pc-cygwin/c++/10"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[SYSROOT]]/usr/lib/gcc/i686-pc-cygwin/10/../../../../include/c++/10/backward"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[SYSROOT]]/usr/local/include"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[RESOURCE]]{{(/|\\\\)}}include"
+// CHECK-SAME: {{^}} "-internal-isystem" "[[SYSROOT]]/usr/lib/gcc/i686-pc-cygwin/10/../../../../i686-pc-cygwin/include"
+// CHECK-SAME: "-internal-externc-isystem" "[[SYSROOT]]/include"
+// CHECK-SAME: {{^}} "-internal-externc-isystem" "[[SYSROOT]]/usr/include"
+// CHECK-SAME: {{^}} "-internal-externc-isystem" "[[SYSROOT]]/usr/include/w32api"
+// CHECK-SAME: "-femulated-tls"
+// CHECK-SAME: "-exception-model=dwarf"
+// CHECK:      "{{.*}}gcc{{(\.exe)?}}"
+// CHECK-SAME: "-m32"
+
+// RUN: %clang -### %s --target=i686-pc-cygwin --sysroot=%S/Inputs/basic_cygwin_tree \
+// RUN:   --stdlib=platform -static 2>&1 | FileCheck --check-prefix=CHECK-STATIC %s
+// CHECK-STATIC:      "-cc1" "-triple" "i686-pc-windows-cygnus"
+// CHECK-STATIC-SAME: "-static-define"
+// CHECK-STATIC:      "{{.*}}gcc{{(\.exe)?}}"
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jeremyd2019 wrote:

yes.  Once you are not calling GCC, you need to teach the driver about the default library search paths (which should already be taken care of), and default libraries, and the startup object files.  Which is probably ultimately necessary, but for now, we can just keep calling gcc.

https://github.com/llvm/llvm-project/pull/135691