builder: interpret linker error messages

This shows nicely formatted error messages for missing symbol names and
for out-of-flash, out-of-RAM conditions (on microcontrollers with
limited flash/RAM).

Unfortunately the missing symbol name errors aren't available on Windows
and WebAssembly because the linker doesn't report source locations yet.
This is something that I could perhaps improve in LLD.

testdata/errors/linker-flashoverflow.go

@@ -0,0 +1,21 @@
+package main
+
+import "unsafe"
+
+const (
+	a = "0123456789abcdef"            // 16 bytes
+	b = a + a + a + a + a + a + a + a // 128 bytes
+	c = b + b + b + b + b + b + b + b // 1024 bytes
+	d = c + c + c + c + c + c + c + c // 8192 bytes
+	e = d + d + d + d + d + d + d + d // 65536 bytes
+	f = e + e + e + e + e + e + e + e // 524288 bytes
+)
+
+var s = f
+
+func main() {
+	println(unsafe.StringData(s))
+}
+
+// ERROR: program too large for this chip (flash overflowed by {{[0-9]+}} bytes)
+// ERROR: 	optimization guide: https://tinygo.org/docs/guides/optimizing-binaries/

testdata/errors/linker-ramoverflow.go

@@ -0,0 +1,9 @@
+package main
+
+var b [64 << 10]byte // 64kB
+
+func main() {
+	println("ptr:", &b[0])
+}
+
+// ERROR: program uses too much static RAM on this chip (RAM overflowed by {{[0-9]+}} bytes)

testdata/errors/linker-undefined.go

@@ -0,0 +1,11 @@
+package main
+
+func foo()
+
+func main() {
+	foo()
+	foo()
+}
+
+// ERROR: linker-undefined.go:6: linker could not find symbol {{_?}}main.foo
+// ERROR: linker-undefined.go:7: linker could not find symbol {{_?}}main.foo