Initial project import

tools/v/cmd/v2/README.md

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+# Run all ARM64 tests
+```
+  ./v run vlib/v2_toberemoved/gen/arm64/tests/run_tests.v
+
+```
+  # Run specific test with test_ssa_backends
+```
+  cd cmd/v2
+  ./test_ssa_backends arm64 ../../vlib/v2_toberemoved/gen/arm64/tests/string_concat.v
+```
+
+  # Or directly with v2
+```
+  ./v2 -backend arm64 ../../vlib/v2_toberemoved/gen/arm64/tests/string_concat.v
+```
+
+# Useful cleanc flags
+```
+  # Disable builtin+strconv object cache for this build:
+  ./v2 -backend cleanc -nocache file.v
+
+  # Print C compiler and link command(s):
+  ./v2 -backend cleanc -showcc file.v
+
+  # Print extended parse/build stats:
+  ./v2 -stats -backend cleanc file.v
+  # Includes per-pass C Gen timing lines to help locate slow codegen phases.
+
+  # Print every parsed file (full and .vh groups):
+  ./v2 -print-parsed-files -backend cleanc file.v
+
+  # Disable markused pruning (emit all functions):
+  ./v2 -nomarkused -backend cleanc file.v
+```
+
+# Eval backend
+```
+  # Execute a small V program directly from the v2 AST:
+  ./v2 -eval file.v
+
+  # Pass runtime args to the interpreted program:
+  ./v2 -eval file.v -- arg1 arg2
+
+  # Self-host under eval without recursively reusing the outer compiler flags:
+  ./v2 -eval cmd/v2/v2.v -- -o /tmp/v2self cmd/v2/v2.v
+
+  # Current scope: literals, locals/consts, plain fn calls, if/for/range,
+  # arrays, indexing, len, println/print, and basic string interpolation.
+```
+
+# SSA C backend (restored)
+```
+  # Run the SSA -> C backend directly:
+  ./v2 -backend c cmd/v2/test.v
+
+  # Compare SSA C output against reference V output:
+  cd cmd/v2
+  ../../v run test_ssa_backends.v c
+```