cmd/go: permit additional cflags when compiling

In CL 475375 the Go command started to generate the "preferlinkext"
token file for "strange/dangerous" compiler flags. This serves as a hint
to the Go linker whether to call the external linker or not.

Permit compiler flags used by bazel and bazelbuild/rules_go during
compilation of cgo code to not prefer external linking. This restores
the behavior of previous versions of Go.

Fixes #60865

Change-Id: I176a6a2a2cf36293dd9aed24be928f98fa2fb6d9
GitHub-Last-Rev: 4127df6
GitHub-Pull-Request: #60868

Author: Holger Hans Peter Freyther

src/cmd/go/internal/work/security.go

@@ -59,7 +59,10 @@ var validCompilerFlags = []*lazyregexp.Regexp{
 	re(`-f(no-)builtin-[a-zA-Z0-9_]*`),
 	re(`-f(no-)?common`),
 	re(`-f(no-)?constant-cfstrings`),
+	re(`-fdebug-prefix-map=([^@]+)=([^@]+)`),
 	re(`-fdiagnostics-show-note-include-stack`),
+	re(`-ffile-prefix-map=([^@]+)=([^@]+)`),
+	re(`-fno-canonical-system-headers`),
 	re(`-f(no-)?eliminate-unused-debug-types`),
 	re(`-f(no-)?exceptions`),
 	re(`-f(no-)?fast-math`),

src/cmd/go/testdata/script/cgo_suspect_flag_force_external.txt

@@ -55,6 +55,19 @@ stderr preferlinkext
 env CGO_CFLAGS=-fprofile-instr-generate
 go build -x -n -o dummy.exe ./usesInternalCgo
 stderr preferlinkext
+
+env CGO_CFLAGS=-fdebug-prefix-map=/some/sandbox/execroot/workspace=/tmp/new
+go build -x -n -o dummy.exe ./usesInternalCgo
+! stderr preferlinkext
+env CGO_CFLAGS=-fdebug-prefix-map=/Users/someone/.cache/bazel/_bazel_someone/3fa7e4650c43657ead684537951f49e2/sandbox/linux-sandbox/10/execroot/rules_go_static=.
+go build -x -n -o dummy.exe ./usesInternalCgo
+! stderr preferlinkext
+env CGO_CFLAGS=-ffile-prefix-map=/Users/someone/.cache/bazel/_bazel_someone/3fa7e4650c43657ead684537951f49e2/sandbox/linux-sandbox/10/execroot/rules_go_static/bazel-out/aarch64-fastbuild-ST-b33d65c724e6/bin/external/io_bazel_rules_go/stdlib_=.
+go build -x -n -o dummy.exe ./usesInternalCgo
+! stderr preferlinkext
+env CGO_CFLAGS=-fdebug-prefix-map=old=/tmp/new -ffile-prefix-map=/Users/someone/_11233/things=new -fno-canonical-system-headers
+go build -x -n -o dummy.exe ./usesInternalCgo
+! stderr preferlinkext
 env CGO_CFLAGS=
 
 [short] skip