ensure CSS placeholders are overwritten

[Rich-Harris]

After #453, CSS started weirding out in Rollup apps, because the chunking algorithm was putting the manifest in a non-entry chunk. Specifically, CSS for pages that are navigated to after the initial load is not fetched.

This fixes it in an admittedly brute-force way. A neater solution would look something like rollup/rollup#2447, but for now this is probably the most appropriate step to take.

(Also, this underscores the need to get some Rollup tests into the test suite — soon, when I'm less busy)

[nsivertsen]

This seems to have broken sapper build --legacy for me:

> EISDIR: illegal operation on a directory, read
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! beige@0.0.1 build: `sapper build --legacy`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the beige@0.0.1 build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/nonscio/.npm/_logs/2018-10-02T14_48_35_675Z-debug.log

Complete log:

0 info it worked if it ends with ok
1 verbose cli [ '/usr/local/bin/node', '/usr/local/bin/npm', 'run', 'build' ]
2 info using npm@6.2.0
3 info using node@v10.1.0
4 verbose run-script [ 'prebuild', 'build', 'postbuild' ]
5 info lifecycle beige@0.0.1~prebuild: beige@0.0.1
6 info lifecycle beige@0.0.1~build: beige@0.0.1
7 verbose lifecycle beige@0.0.1~build: unsafe-perm in lifecycle true
8 verbose lifecycle beige@0.0.1~build: PATH: /usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/node-gyp-bin:/Users/nonscio/source/beige/node_modules/.bin:/Users/nonscio/npm/bin:/Users/nonscio/.composer/vendor/bin:/Users/nonscio/bin:/Users/nonscio/.cargo/bin:/Users/nonscio/.luarocks/bin:/Users/nonscio/.nix-profile/bin:/Users/nonscio/.nix-profile/lib/kde4/libexec:/nix/var/nix/profiles/default/bin:/nix/var/nix/profiles/default:/nix/var/nix/profiles/default/lib/kde4/libexec:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/plan9/bin
9 verbose lifecycle beige@0.0.1~build: CWD: /Users/nonscio/source/beige
10 silly lifecycle beige@0.0.1~build: Args: [ '-c', 'sapper build --legacy' ]
11 silly lifecycle beige@0.0.1~build: Returned: code: 1  signal: null
12 info lifecycle beige@0.0.1~build: Failed to exec build script
13 verbose stack Error: beige@0.0.1 build: `sapper build --legacy`
13 verbose stack Exit status 1
13 verbose stack     at EventEmitter.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/index.js:304:16)
13 verbose stack     at EventEmitter.emit (events.js:182:13)
13 verbose stack     at ChildProcess.<anonymous> (/usr/local/lib/node_modules/npm/node_modules/npm-lifecycle/lib/spawn.js:55:14)
13 verbose stack     at ChildProcess.emit (events.js:182:13)
13 verbose stack     at maybeClose (internal/child_process.js:957:16)
13 verbose stack     at Process.ChildProcess._handle.onexit (internal/child_process.js:246:5)
14 verbose pkgid beige@0.0.1
15 verbose cwd /Users/nonscio/source/beige
16 verbose Darwin 17.7.0
17 verbose argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "build"
18 verbose node v10.1.0
19 verbose npm  v6.2.0
20 error code ELIFECYCLE
21 error errno 1
22 error beige@0.0.1 build: `sapper build --legacy`
22 error Exit status 1
23 error Failed at the beige@0.0.1 build script.
23 error This is probably not a problem with npm. There is likely additional logging output above.
24 verbose exit [ 1, true ]

sapper dev works fine, though.

[Rich-Harris]

oops. working on it...

[Rich-Harris]

I just released a fix 🤞

[nsivertsen]

That did it, thanks for the quick fix!